A. Skin patch test – Explanation
Allergy tests
| Skin prick test | Most commonly used test as easy to perform and inexpensive. Drops of diluted allergen are placed on the skin after which the skin is pierced using a needle. A large number of allergens can be tested in one session. Normally includes a histamine (positive) and sterile water (negative) control. A wheal will typically develop if a patient has an allergy. Can be interpreted after 15 minutes Useful for food allergies and also pollen |
| Radioallergosorbent test (RAST) |
Determines the amount of IgE that reacts specifically with suspected or known allergens, for example IgE to egg protein. Results are given in grades from 0 (negative) to 6 (strongly positive)
Useful for food allergies, inhaled allergens (e.g. Pollen) and wasp/bee venom
Blood tests may be used when skin prick tests are not suitable, for example if there is extensive |
| Skin patch testing | Useful for contact dermatitis. Around 30-40 allergens are placed on the back. Irritants may also be tested for. The patches are removed 48 hours later with the results being read by a dermatologist after a further 48 hours |
