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The coronavirus disease 2019 (COVID-19) pandemic is caused by rapid spread of different strains of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The severity of infection ranges from mild, or even asymptomatic, to very severe. Signs and symptoms include fatigue, fever, exanthemas, upper respiratory illness, loss of smell and taste, pneumonia, severe acute respiratory syndrome, and multi-organ failure. Risk factors for a severe or lethal course include age, male gender, obesity, diabetes, cardiovascular disease, and immune suppression1 .

Author(s): Thyssen, JP; de Bruin-Weller, MS; Paller, AS; Leshem, YA; Vestergaard, C; Deleuran, M; Drucker, AM; Foelster-Holst, R; Traidl-Hoffmann, C; Eyerich, K; Taieb, A; Su, JC; Bieber, T; Cork, MJ; Eichenfield, LF; Guttman-Yassky, E; Wollenberg, A | Abstract: BackgroundConjunctivitis is common in patients with atopic dermatitis (AD) in general and a commonly reported adverse event in AD clinical trials with dupilumab.ObjectiveTo survey opinions and experience about conjunctivitis occurring in AD, including those during dupilumab treatment in a group of AD experts from the International Eczema Council (IEC).MethodsElectronic survey and in-person discussion of management strategies.ResultsForty-six (53.5%) IEC members from 19 countries responded to the survey. Consensus was reached for several statements regarding diagnostic workup, referral and treatment. IEC members suggest that patients with AD should (i) routinely be asked about ocular complaints or symptoms, (ii) obtain information about the potential for conjunctivitis before starting dupilumab therapy and (iii) if indicated, be treated with dupilumab despite previous or current conjunctivitis. In cases of new-onset conjunctivitis, there was consensus that dupilumab treatment should be continued when possible, with appropriate referral to an ophthalmologist.LimitationsThe study relies on expert opinion from dermatologists. Responses from few dermatologists without dupilumab access were not excluded from the survey.ConclusionThe IEC recommends that dermatologists address conjunctivitis in patients with AD, especially during treatment with dupilumab.

Summary Background Dupilumab blocks the shared receptor component for interleukin (IL)‐4 and IL‐13. It is approved in the U.S.A. for patients aged ≥ 12 years with moderate‐to‐severe atopic dermatitis (AD) uncontrolled by topical prescription medicines or who cannot use topical medicines, for patients in Japan whose AD is uncontrolled with existing therapies, for patients with moderate‐to‐severe AD in Europe who are candidates for systemic therapy and for patients aged ≥ 12 years for maintenance treatment of moderate‐to‐severe asthma uncontrolled with their current medicines. AD trials have reported increased incidence of conjunctivitis for dupilumab vs. placebo. Objectives To characterize further the occurrence and risk factors of conjunctivitis in dupilumab clinical trials. Methods We evaluated randomized placebo‐controlled trials of dupilumab in AD (n = 2629), asthma (n = 2876), chronic rhinosinusitis with nasal polyps (CRSwNP) (n = 60) and eosinophilic oesophagitis (EoE) (n = 47). Results In most AD trials, dupilumab‐treated patients had higher conjunctivitis incidence than placebo controls. Higher baseline AD severity and previous history of conjunctivitis were associated with increased conjunctivitis incidence. Conjunctivitis was mostly mild to moderate. Most cases recovered or resolved during the treatment period; two patients permanently discontinued dupilumab due to conjunctivitis or keratitis. Common treatments included ophthalmic corticosteroids, antibiotics, and antihistamines or mast cell stabilizers. Most cases were diagnosed by the investigators. In asthma and CRSwNP trials, the incidence of conjunctivitis was lower for both dupilumab and placebo than in AD trials; dupilumab did not increase the incidence compared with placebo. In the EoE trial, no patients had conjunctivitis. Conclusions Conjunctivitis was more frequent with dupilumab treatment in most AD trials. In dupilumab trials in other type 2 diseases, incidence of conjunctivitis was overall very low, and was similar for dupilumab and placebo. In AD, the incidence of conjunctivitis was associated with AD severity and prior history of conjunctivitis. The aetiology and treatment of conjunctivitis in dupilumab‐treated patients require further study. What's already known about this topic? Ocular disorders, including allergic conjunctivitis, are common in patients with atopic dermatitis (AD).In most dupilumab AD trials, dupilumab‐treated patients had higher conjunctivitis incidence than those receiving placebo.Most cases were mild to moderate and recovered or were recovering during study treatment; study treatment discontinuation due to conjunctivitis was rare.Conjunctivitis incidence was very low and similar for dupilumab and placebo in clinical trials in asthma, chronic rhinosinusitis with nasal polyps and eosinophilic oesophagitis. What does this study add? This analysis confirms and extends the results of the individual clinical trials.Baseline disease‐related factors, including AD severity, prior conjunctivitis history and certain biomarkers (thymus and activation‐regulated chemokine, IgE, eosinophils), were associated with increased incidence of conjunctivitis.Patients who responded well to dupilumab had reduced incidence of conjunctivitis.Further study is needed to elucidate the aetiology and treatment of conjunctivitis in dupilumab‐treated patients with AD., Linked Editorial: https://doi.org/10.1111/bjd.18255. https://doi.org/10.1111/bjd.18276 available online https://www.bjdonline.com/article/

Since the introduction of active vaccination against SARS-CoV-2 infection, there has been a debate about the risk of developing severe allergic or anaphylactic reactions among individuals with a history of allergy. Indeed, rare cases of severe allergic reactions have been reported in the United Kingdom and North America. By february 2021 a rate of 4,5 severe allergic reactions occurred among 1 million patients vaccinated with the mRNA-based COVID-19 vaccines, which is higher than the generally expected rate of severe allergic reactions to vaccinations of around 1 in 1 million.

Summary Background Guidelines discourage the use of systemic corticosteroids for atopic dermatitis (AD), but their use remains widespread. Objectives To reach consensus among an international group of AD experts on the use of systemic corticosteroids for AD. Methods A survey consisting of statements accompanied by visual analogue scales ranging from ‘strongly disagree’ to ‘neutral’ to ‘strongly agree’ was distributed to the International Eczema Council (IEC). Consensus was reached in agreement on a statement if, What's already known about this topic? Despite recommendations against their use in practice guidelines, systemic corticosteroids are commonly used for atopic dermatitis (AD). What does this study add? The International Eczema Council reached consensus on circumstances in which systemic corticosteroids can be used for AD, including a lack of other treatment options, as a bridge to other systemic therapies or phototherapy, during acute flares in need of immediate relief, in anticipation of a major life event, or in the most severe cases.Clinicians should limit the use of systemic corticosteroids for severe AD to those circumstances. https://doi.org/10.1111/bjd.16385 available online https://goo.gl/Uqv3dl

Azathioprine is frequently used in severe eczema. It is converted in the liver into active metabolites, including 6-thioguanine nucleotide (6-TGN) and methylated 6-methylmercaptopurine (6-MMP). In the past, the therapeutic potential of azathioprine may have not been fully utilized. Recent investigations on inflammatory bowel disease have led to a better understanding of azathioprine metabolism and optimizing treatment.To investigate whether measuring thiopurine metabolites in circulation can improve the effectiveness and safety of azathioprine treatment in patients with atopic dermatitis and/or chronic hand/foot eczema.Azathioprine metabolite levels were measured in eczema patients during maintenance treatment (Part I) and dose escalation (Part II). Clinical effectiveness, hepatotoxicity, and bone marrow suppression were analyzed and TPMT genotype was assessed.A wide variation in metabolite levels in all dose groups was observed. In Part I (32 patients), there were no significant differences in 6-TGN levels between clinical responders and non-responders (p = .806). No hepatoxicity or myelotoxicity was observed. In Part II, all 6-TGN and 6-MMP levels increased during dose escalation. Hypermethylation was observed in 2/8 patients.For individual eczema patients treated with azathioprine, routinely measuring 6-TGN and 6-MMP can be helpful in optimizing azathioprine dose, improving clinical effectiveness, and preventing side effects.

Summary Background For many years dermatologists have had access to few therapies for patients with moderate‐to‐severe atopic eczema (AE). New promising therapies are entering the market but conventional phototherapies and systemic therapies have more well‐known safety profiles, lower costs and wider availability. Objectives To provide insight into current prescribing practices of conventional phototherapy and systemic immunomodulatory therapies for adults with chronic AE, and the factors influencing these prescribing practices, before biologics and other novel therapeutics become routine clinical practice. Methods In this exploratory study dermatologists were invited to participate in an online survey via a mailing list of the European Academy of Dermatology and Venereology and national societies. Data were collected on participant characteristics (including clinical practice data), the use of phototherapies and systemic therapies, and factors influencing their use. Results From 30 European countries, 238 out of 361 dermatologists willing to participate (65·9%) completed the survey, with 229 meeting the inclusion criteria. For phototherapy (prescribed by 84·7%), most preferred narrowband ultraviolet B as first line (80·9%) and psoralen plus ultraviolet A as second (21·6%). For systemic therapy (prescribed by 95·2%) ciclosporin (54·1%), oral corticosteroids (32·6%) and methotrexate (30·7%) were used first line. Dermatologists relied mostly on personal experience for prescribing phototherapy and systemic therapy. Azathioprine and mycophenolic acid were prescribed by only 135 (59·0%) and 85 (37·1%) participants in total, mostly due to a lack of personal experience. Conclusions This study provides insight into prescribing practices for conventional phototherapy and systemic therapy in Europe and shows that off‐label therapies are also preferred as first‐line choice of systemic therapy., What is already known about this topic? Varying prescribing practices were found for adult (in the UK) and paediatric (in Northern America and Europe) patients with moderate‐to-severe atopic eczema (AE).Not much is known about the prescription of phototherapy and (off‐label) systemic therapy for adult patients in Europe.Although therapies like dupilumab are promising new treatment modalities, better‐known safety profiles, lower costs and better availability are reasons to improve the evidence profile of conventional systemic therapies like ciclosporin. What does this study add? Prescribing practices of European dermatologists treating adult patients with moderate‐to-severe AE show diversity.Most dermatologists prefer narrowband ultraviolet B as first‐line phototherapy, followed by psoralen plus ultraviolet A as second line.Next to ciclosporin, which is most commonly prescribed, (off‐label) methotrexate and oral corticosteroids are also frequently used as first‐line systemic agents in chronic AE.Lack of personal experience with azathioprine and mycophenolic acid was the most important reason against their prescription. What are the clinical implications of the work? The results from this study might help to improve the experience with, and prescribing of, all available conventional phototherapies and (off‐label) systemic therapies.Guidelines developers might use these results to develop and implement treatment algorithms. Linked Comment: Bruin‐Weller. Br J Dermatol 2020; 183:987–988. Plain language summary available online

Results from clinical studies indicate that azathioprine and enteric-coated mycophenolate sodium (EC-MPS) are safe and potent drugs in the treatment of atopic dermatitis (AD).(1-5) However, published data from large groups of non-selected patients is non-existent to date which hampers generalization to daily practice. In addition, head-to-head trials in which azathioprine and EC-MPS are compared, have never been performed. The primary objective was to perform an analysis of drug survival for azathioprine and EC-MPS in a long-term daily practice cohort of patients with AD. The secondary objective was to identify determinants of drug survival. This article is protected by copyright. All rights reserved.

Summary Background The Dermatology Department of the University Medical Centre Utrecht, the Netherlands, developed an e-health portal for patients with atopic dermatitis (AD), consisting of e-consultation, a patient-tailored website, monitoring and self-management training. Objectives To determine the cost-effectiveness of individualized e-health compared with usual face-to-face care for children and adults with AD. Methods A randomized controlled cost-effectiveness study from a societal perspective in adults and parents of children with moderate AD. Outcomes were quality of life, severity of AD, itching and direct and indirect costs. Data were collected at baseline and at 3 and 12 months after randomization. Linear mixed models were used to analyse clinical outcomes. After multiple imputation of missing data, costs and differences in costs were calculated over a period of 1 year. Results In total, 199 patients were included. There were no significant differences in disease-specific quality of life, severity of AD and intensity of itching between both groups at the three time points. The difference in direct costs between the intervention and control groups was €24 [95% confidence interval (CI) −360 to 383], whereas this difference was −€618 (95% CI −2502 to 1143) for indirect costs. Overall, individual e-health was expected to save €594 (95% CI −2545 to 1227) per patient in the first year of treatment, mainly through a reduction in work absenteeism. Uncertainty analyses revealed that the probability of e-health reducing costs was estimated to be ≥ 73%. Conclusions E-health during follow-up of patients with AD is, after initial diagnosis and treatment during face-to-face contact, just as effective as usual face-to-face care with regard to quality of life and severity of disease. However, when costs are considered, e-health is likely to result in substantial cost savings. Therefore, e-health is a valuable service for patients with AD.

Atopic dermatitis is a chronic inflammatory skin disease that may require systemic therapy. Ciclosporin A (CsA) is a widely used, potent immunosuppressant but it is not effective in all patients with atopic dermatitis, and side-effects limit its use. Dupilumab, a fully human anti-interleukin 4 receptor-alpha monoclonal antibody, inhibits signaling of IL-4 and IL-13, key drivers of Type 2/Th2-mediated inflammation, and is approved in the U.S.A. and the European Union for the treatment of inadequately-controlled moderate-to-severe atopic dermatitis in adults.To evaluate efficacy and safety of dupilumab with concomitant topical corticosteroids (TCS) in adults with atopic dermatitis with inadequate response to/intolerance of CsA, or for whom CsA treatment was medically inadvisable.In this 16-week, double-blind, randomized, placebo-controlled, phase III trial, patients were randomized 1 : 1 : 1 to subcutaneous dupilumab 300 mg weekly (qw) or every 2 weeks (q2w) or placebo. All received concomitant medium-potency TCS from Week -2 through Week 16; dosage could be tapered if lesions cleared, or stopped for adverse reactions to TCS.In total, 390 patients were screened, 325 were randomized, and 318 completed the trial. Treatment groups had similar baseline characteristics. Significantly more patients in the dupilumab qw + TCS and q2w + TCS groups achieved ≥ 75% improvement from baseline in the Eczema Area and Severity Index at Week 16 vs. the placebo + TCS group (primary end point) (59·1% and 62·6% vs. 29·6%, respectively; P0·001 vs. placebo + TCS, both doses). Other clinical outcomes and atopic dermatitis symptoms were significantly improved in the dupilumab qw + TCS and q2w + TCS groups, including pruritus, pain, sleep disturbance, symptoms of anxiety and depression, and quality of life (QoL). Treatment groups had similar overall rates of adverse events (qw + TCS, q2w + TCS and placebo + TCS groups: 69·1%, 72·0% and 69·4%, respectively) and serious adverse events (1·8%, 1·9% and 1·9%, respectively). Conjunctivitis was more frequent with dupilumab + TCS; skin infections were more frequent with placebo + TCS.Dupilumab + TCS significantly improved signs and symptoms of atopic dermatitis and QoL in adults with a history of inadequate response to/intolerance of CsA, or for whom CsA treatment was medically inadvisable. No new safety signals were identified.

Summary Background Atopic dermatitis (AD) is a chronic inflammatory skin disease commonly treated with topical corticosteroids. The inflammatory nature of this disorder and the use of topical corticosteroids represent potential risk factors for bone loss. Objectives The aim was to assess the prevalence of osteoporosis and osteopenia in adult patients with moderate to severe AD. In addition, the associations between topical/oral corticosteroid use and bone mineral density (BMD) and between disease activity and BMD were studied. Patients and methods We studied 125 adult patients with moderate to severe AD. Using dual-energy X-ray absorptiometry, BMD was measured at lumbar spine and hips. The cumulative dose of topical and oral corticosteroids was calculated from pharmacy prescription records. Lifestyle parameters were collected by a questionnaire. Biochemical parameters of bone metabolism and disease activity [serum concentration of thymus and activation-regulated chemokine (TARC) levels] were also measured. Results Osteoporosis was documented in six patients (4·8%) and osteopenia in 41 patients (32·8%); 30·4% of the patients had a Z-score ≤ −1 (low BMD), with more men (43·8%) than women (16·4%) affected. There was no significant association between low BMD and biochemical parameters of bone metabolism, serum TARC levels and cumulative dose of topical and oral corticosteroids during the 5 years prior to inclusion. Conclusions We document a Z-score ≤ −1 in about one-third of predominantly male patients with moderate to severe AD, being independent of the cumulative dose of topical and corticosteroids used within 5 years prior to study. Whether the relatively high prevalence of low BMD is due to the cumulative dose of topical corticosteroids beyond 5 years prior to the study or the chronicity of the underlying inflammatory process or a combination of these, remains to be established.

Background Cyclosporin A (CsA) is being increasingly used in the treatment of severe refractory atopic dermatitis. Clinical efficacy and safety of short-term cyclosporin A treatment in atopic dermatitis patients has been proven, however, data on long-term treatment are limited. Objective The aim of this study was to investigate the efficacy, safety and the effect of discontinuation of cyclosporin A treatment in atopic dermatitis patients, with a particular focus on patients treated with cyclosporin A for more than 6 months. Methods We performed a retrospective study of clinical and adverse effects of cyclosporin A treatment in 73 atopic dermatitis patients, with an average duration of cyclosporin A treatment of 1.3 years. Results We included 73 patients (31 women and 42 men, with a mean age of 33.8 years) with severe atopic dermatitis refractory to conventional therapy that was treated with cyclosporin A. Treatment was successful in 56/73 patients. Increases in serum creatinine levels > 30% compared to baseline were reported in 7/73 patients. Arterial hypertension appeared in 11/73 patients during treatment. After discontinuation of treatment, 40/73 patients experienced a relapse and 33/73 patients experienced clinical remission for at least 3 months. No correlation between treatment duration and nephrotoxicity or hypertension was found. Strikingly, 6/73 patients experienced a rebound phenomenon. Conclusions We conclude that CsA is an effective and safe treatment for patients with severe AD refractory to conventional treatment, provided that the recommended guidelines for its administration are strictly observed. However, in contrast to previous reports, we found that 8% (6/73) of patients experienced a rebound phenomenon after discontinuation of treatment.

Background: The atopy patch test (APT) is an in vivo model to study the induction of eczema by inhalant allergens in atopic dermatitis patients. We studied the effect of pretreatment with topical tacrolimus 0.1% on APT in nonlesional skin of patients with atopic dermatitis. Methods: Nonlesional skin of the back of patients with atopic dermatitis (n = 8) was treated once daily for 3 weeks with tacrolimus 0.1% ointment. Cetomacrogol ointment (placebo) was used as a negative control and triamcinolone acetonide 0.1% ointment as positive control. Twenty-four hours after the last APT application, samples were taken from the three treated areas (t = 0 and 24 h) for immunohistochemical analysis. Results: Pretreatment with tacrolimus ointment did not suppress nonlesional skin infiltrate, in contrast to triamcinolone acetonide. Furthermore, tacrolimus did not inhibit the induction of the APT macroscopically (t = 24 h). An equal influx of T cells, eosinophils, dendritic cells, CD64+ and FcɛRI-positive cells was present compared with placebo. Only CD36+ and CD68-positive cells were inhibited compared with placebo. All cell types were significantly inhibited in triamcinolone acetonide-treated sites compared with placebo. Conclusions: Pretreatment with tacrolimus 0.1% ointment does not inhibit the APT reaction in patients with atopic dermatitis.

Background: The atopy patch test (APT) is an in vivo model to study the induction of eczema by inhalant allergens. This study was designed to compare two commonly used APT methods. Methods: In the first method, the allergen is dissolved in aqueous solution, which is applied on tape-stripped skin. In the second method, the allergen is dissolved in petrolatum and applied without tape stripping. Thirteen patients with atopic dermatitis sensitized to inhalant allergens were patch tested using both methods. Reactions were evaluated macroscopically and microscopically after 48 h. Results: Nine out of 13 patients displayed a positive reaction for both methods. One patient had a positive APT for the aqueous method alone and three for the petrolatum method alone. Reactions were significantly stronger when using the petrolatum method. Histological evaluation of the nine patients positive for both methods showed no significant differences in number of eosinophils, T-cells and neutrophils. Conclusion: The APT using the petrolatum vehicle induces a higher number of positive reactions and is significantly stronger relative to the APT using allergen in aqueous vehicle. The cellular influx in both test methods is comparable. Both methods can be used to study the mechanisms in the induction of eczema by inhalant allergens.

Background Anti-allergic mattress encasing may provide clinical benefit in asthmatic patients. However, the effect of mattress encasings on allergen-specific parameters, such as bronchial reactions to house dust mite (HDM) challenge, is not clear. Objective To investigate the effect of anti-allergic mattress encasings on allergen sensitivity in patients with moderate to severe asthma. Methods Twenty-seven patients with asthma and HDM allergy were studied in a double-blind, placebo-controlled study. Concentrations of Dermatophagoides pteronyssinus (Der p 1) were measured in mattress dust before and after 1 year of treatment; bronchial histamine challenge, bronchial challenge with HDM and intradermal skin challenges with HDM were performed. The number of eosinophils in peripheral blood was assessed. Results In the active group, but not in the placebo group, there was a significant reduction in Der p 1 concentration in the dust collected from the mattresses after 1 year of treatment compared to before. There was a significant difference between the groups with respect to HDM-induced early-reaction (ER) in the airways and the number of blood eosinophils, which reflected an increase in ER and eosinophils in the placebo group without significant change in the active group. No significant improvement in PC20 histamine, late-reaction (LR) and skin tests was found in either groups. Conclusion Our data suggest that encasings protect against a further increase in allergen sensitivity in asthmatic patients, so their use should be recommended.

Studies assessing the relationship between disease activity and quality of life (QoL) in adults with atopic dermatitis (AD), before and after therapy are lacking. The relation between disease activity and QoL in AD patients was evaluated before (t = 0) and after 6 weeks (t = 6) of treatment with cyclosporin 5 mg/kg.In 54 patients with severe AD, disease activity was assessed using objective Scoring Atopic Dermatitis index (SCORAD), Six Area Six Sign Atopic Dermatitis (SASSAD), 'rule of nines' extent score and serum levels of thymus and activation-regulated chemokine (TARC). Patients filled out the Dermatology Life Quality Index (DLQI). To study the relation between disease activity and QoL, correlations were calculated and regression analysis was performed.At t = 0 there was a small, non-significant correlation between the DLQI and the objective SCORAD, 'rule of nines' or serum TARC levels. At t = 6 the objective SCORAD, serum TARC and the 'rule of nines' score showed moderate and significant correlations with the DLQI (r = 0.34, P = 0.02; r = 0.31, P = 0.03; r = 0.49, P0.001). An individual's improvement in disease activity (objective SCORAD, SASSAD and 'rule of nines') with 10 points was associated with an improvement of 1.3, 1.5 and 1.1 points respectively in DLQI.Disease activity correlated better with QoL when disease activity was less severe and disease extent ('rule of nines') correlated better with QoL than disease severity. An individual's improvement of 10 points in disease activity was accompanied by only a small improvement in QoL. Other factors than disease activity may influence QoL in patients with AD.

Azathioprine (AZA) is a purine antagonist, which is frequently used off label in chronic inflammatory skin diseases. Genetic polymorphisms in thiopurine S-methyltransferase (TPMT) influence the metabolism of AZA. A reduced enzymatic activity of TMPT is associated with increased 6-thioguaninie nucleotide (6-TGN) levels which may cause severe leukopenia. High TPMT activity is associated with increased 6-methylmercaptopurine (6-MMP) levels (toxic 6-MMP >5700 pmol/8x10(8) RBCs), which is associated with liver toxicity.(1) Alanine transaminase (ALT) >3 upper limits of normal has been identified as a sensitive, but not necessarily specific signal of liver toxicity.(2) In daily practice AZA is often started with a test dose of 50 mg/day for 1-2 weeks. If laboratory tests show no abnormalities, the dose is increased to up to 150-200 mg/day. This article is protected by copyright. All rights reserved.

Anti-allergic mattress encasing may provide clinical benefit in asthmatic patients. However, the effect of mattress encasings on allergen-specific parameters, such as bronchial reactions to house dust mite (HDM) challenge, is not clear.To investigate the effect of anti-allergic mattress encasings on allergen sensitivity in patients with moderate to severe asthma.Twenty-seven patients with asthma and HDM allergy were studied in a double-blind, placebo-controlled study. Concentrations of Dermatophagoides pteronyssinus (Der p 1) were measured in mattress dust before and after 1 year of treatment; bronchial histamine challenge, bronchial challenge with HDM and intradermal skin challenges with HDM were performed. The number of eosinophils in peripheral blood was assessed.In the active group, but not in the placebo group, there was a significant reduction in Der p 1 concentration in the dust collected from the mattresses after 1 year of treatment compared to before. There was a significant difference between the groups with respect to HDM-induced early-reaction (ER) in the airways and the number of blood eosinophils, which reflected an increase in ER and eosinophils in the placebo group without significant change in the active group. No significant improvement in PC20 histamine, late-reaction (LR) and skin tests was found in either groups.Our data suggest that encasings protect against a further increase in allergen sensitivity in asthmatic patients, so their use should be recommended.

Repeated allergen challenge might be a more relevant model for studying symptomatic disease, because it gives more information on the patient's handling of chronic allergen exposure. Thus, this experimental model has more resemblance to the situation of natural allergen exposure, and the allergen load can be standardized. However, the response to repeated allergen challenge in individual patients can show a large variation, that is from a strongly enhanced response to complete diminution of the response. Successful allergen immunotherapy can change the response pattern of repeated allergen challenge in the skin into down-regulation of the late reaction. Chronic or repeated allergen exposure may result in an enhanced allergen-specific allergic response, involving allergen-specific T-cell activation. Different subsets of T cells can exert either activating or suppressive effects on inflammatory cells involved in subsequent allergic reactions. CD8+ T cells might exert suppressive effects, because they seem to be associated with a subsequent down-regulation of the late skin reaction after repeated allergen challenge (Fig. 4). Further studies are needed to compare the responses to repeated allergen challenge with the response to natural seasonal allergen exposure in the same patients and to explore possible underlying mechanisms using, for example, nasal biopsies.