Skin prick testing in urticaria

Skin prick testing (SPT)

• allergic reactions to foods are rarely the cause of chronic urticaria but patients are often referred to hospital in the belief that foods are responsible
  • a practical approach is to start by excluding an atopic diathesis by undertaking skin prick tests (SPTs) to a panel of aeroallergens
    • if negative, this significantly reduces the likelihood of an IgE-mediated allergic reaction to foods and other allergens
• additional skin testing can also be helpful to some of the foods that the patient suspects as the cause of their urticaria
  
  
• the sight of a negative SPT helps to reassure the patient that allergy is not the cause of their symptoms and may contribute to improved concordance with long-term antihistamines
  • however, foods may be responsible for the symptoms of acute intermittent urticaria, for example wheat followed by exercise can cause urticaria/angio-oedema and even anaphylaxis
    • in this situation the patient is often atopic and has a positive SPT and/or specific IgE to the implicated food

Reference:

• (1) Powell RJ et al; British Society for Allergy and Clinical Immunology (BSACI). BSACI guidelines for the management of chronic urticaria and angio-oedema.Clin Exp Allergy. 2007 May;37(5):631-50.