Contact urticaria is a different type of allergy, which can also occur at any time.
The reaction starts immediately following contact with the allergen, usually within 10-30 minutes following skin contact. It normally settles down an hour after contact has stopped. It is usually caused by a plant or animal product.
This condition usually causes welts or hives on the skin, with itchiness and swelling, but can also cause a runny nose, sneezing and asthma like symptoms.
Recurrent episodes of contact urticaria can lead to dermatitis (termed protein contact dermatitis). This may appear just like allergic or irritant contact dermatitis.
Special blood tests and a different form of allergy testing, prick testing, is used to diagnose contact urticaria. Prick testing is commonly used by allergists to diagnose causes of asthma, hayfever and food allergies. Blood tests (radioallergosorbent or RAST) can also be used. Latex allergy is a form of contact urticaria.