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

BSACI have SOP.

Anergy is the failure for testing to confirm allergy after a recent severe reaction – this is well recognised with venom allergy but in theory could affect both skin prick and IgE testing within a few weeks/months of a reaction.