Skin prick allergen

Specimen:

In vivo procedure which should only be performed by an experienced practitioner.

Anaphylaxis is a rare complication.

Method:

Intra-epidermal injection of minute amounts of standardised glycerinated antigen solutions.

Negative (diluent) and positive (histamine acid phosphate) controls must be included with each test.

Reference Interval:

Wheal > 3 mm is positive, provided that the negative control is non-reactive.

Application:

Investigation of reactions to inhalants, insect venoms, and foods.

Interpretation:

A positive reaction indicates the presence of specific IgE antibody to the antigen administered. This may or may not correlate with clinical allergy to the material.

Positive reactions to multiple antigens indicate an atopic state. Positive reactions to the negative control and all antigens suggest dermatographia.

A negative reaction to the positive control suggests interference by drugs eg, antihistamines. Corticosteroids do not interfere with the test.

Reference:

Li JT. Am Fam Physician 2002; 66(4): 621-624.