Not great, particularly in young infants, but probably the best method of testing for type 1 allergy other than direct challenge.

You do need a patch of healthy skin however, so if bad eczema all over then not an option. Easiest is the medial forearm, but failing that, the back.

Some medicines interfere with skin prick testing (suppress it) – most commonly antihistamines. Non sedating should ideally be stopped 7 days before testing, sedating 48 hours. Other problem medicines are:

• Azelastine nasal spray (48 hours)
• Steroids – some say short courses ok
• Tricyclic antidepressants (7-14 days) but not SSRIs
• Benzodiazepines!
• Ranitidine (48 hours)! But not omeprazole
• Omalizumab, obviously (6 months)
• Topical tacrolimus yes, pimecrolimus no!?
• Ciclosporin is ok