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Background: Cross‐reactivity among beta‐lactam antibiotics (BL) is essentially reported in immediate hypersensitivity. Objectives: To evaluate cross‐reactivity beyond BLs in patients with non‐immediate cutaneous adverse drug reaction (non‐immediate CADR) managed in a dermatology reference centre of toxic bullous and severe CADRs. Patients/Materials/Methods: We conducted a retrospective single‐centre study in consecutive patients consulting between 2010 and 2018 with an active BL‐suspected non‐immediate CADR and explored by cutaneous tests [patch tests (PT) and intradermal tests (P‐IDR)] for at least three penicillin's subclasses and amino‐ and non‐amino‐cephalosporins (at least one aminocephalosporin). Cross‐reactivity among subclasses was investigated for patients with positive tests. Results: We included 56 patients, among whom 46 amoxicillin‐suspected were and seven cephalosporin‐suspected. Twenty‐nine had severe CADR, and 27 had non‐immediate maculopapular exanthema (MPE). Twenty‐two had positive tests (18 for AS and four for CS). Among the 18 positive amoxicillin‐suspected, 10 (55.6%) showed cross‐reactivity with one or more other BL: 9 (50%) with another penicillin and 3 (16.5%) with a non‐aminocephalosporin. No amoxicillin‐ or cephalosporin‐suspected patient showed cross‐reactivity with aztreonam or carbapenems. P‐IDR showed cross‐reactivity only once. Conclusion: After a suspected BL‐induced non‐immediate CADR, a large allergologic exploration is needed to confirm the diagnosis and evaluate cross‐reactivity. In our population including cases of severe CADRs and MPE with late delay of onset, cross‐reactivity was frequent and PT was sufficient to this purpose. The frequent cross‐reactivity among penicillins encourages stopping this whole family and to test cephalosporins, aztreonam and carbapenems for which cross‐allergies are rarer. [ABSTRACT FROM AUTHOR]