Urticaria Special examination:
① Skin scratch syndrome test
It is commonly used to diagnose skin scratch syndrome type urticaria. Use a blunt object to scratch the surface of the patient's skin with appropriate pressure. Since the patient can cause a strong physiological reaction to a weak external stimulus, the following triple reaction may occur:
1) 3-15 seconds after the scratch, the scratched area will appear. Red line;
2) After 15-45 seconds, redness appears on both sides of the red line;
3) 1-3 minutes after the stroke, raised, pale wheal-like lines appear on the skin.
1. Ice cube test: Put the ice cube into a general hot water bottle (do not put ice in contact with the skin for the purpose of waterborne urticaria identification), then place it on the forearm and keep it in contact with the skin for about 20 minutes. The positive person will If erythema and wheals appear, this is an immediate cold allergy. However, for delayed cold allergy, the ice test can be positive within 24 hours or 48 hours.
2. Cold water test: First place one arm in water of 8-10℃ for 5-15 minutes. If no erythema or wheal appears, it can be placed in water of 21℃. If it is still negative, the patient can Take a cold shower. However, this test cannot easily differentiate between aquagenic urticaria and cold urticaria.
c. Cold air test: If the patient's ice cube test and cold water test are both negative, a cold air exposure test can be performed, that is, the patient is placed in a low-temperature room (4°C). If the patient is positive, wheals will appear soon after chills, or observation If erythema or wheal appears after 10 minutes, it is considered positive.
Differential diagnosis of urticaria
1. Erythema multiforme: also known as exudative erythema. Clinical manifestations: Before the rash, there is often mild discomfort such as low fever and sore throat, followed by sudden onset of skin lesions, which are symmetrically distributed on the back of the hands, the back of the feet, the forearms and the extensor sides of the calves, both sides of the face and cheeks, and can develop upward from the ends of the limbs. It can also accumulate on the lips, oral mucosa, conjunctiva, and external genitalia.
2, pruritus : It is a common skin disease. Scratching will produce skin lesions similar to scratches, and some will leave small nodules similar to pruritus . The difference between this disease and urticaria is that although urticaria is very itchy and the itching is obvious after scratching, it rarely leaves traces or pigmentation after it subsides, while pruritus often leaves linear and circular scratches after scratching. The skin is rough, desquamated or has papules, small nodules, etc.
3. Contact allergic dermatitis of the eyelids: Contact dermatitis of the eyelids can also cause high eyelid edema and limited eye opening. The main difference from urticaria is that allergic contact dermatitis has a recent history of chemical exposure; in addition to local swelling, the clinical manifestations usually include exudation, small blisters, and desquamation, which last for a long time.
4, Erysipelas , cellulitis, etc.: Erysipelas, cellulitis, etc. can also cause deep tissue edema and are often easily confused with angioedema. However, in addition to local edema, the former also has local symptoms of redness, swelling, heat, and pain.
