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Urticaria and hives
The clinical manifestations are sudden onset of red colored wheals which may be associated with swelling of the lips and eyes.

Types of allergic reactions
Physical Urticarias can be triggered off by gentle stroking of the skin or even by exposure to heat or cold (Cholenergic Urticaria) or rarely by contact with water (Aquagesic Urticaria).
Immunologic Urticaria is triggered by allergy to drugs, food, insect bites, or intestinal infestation with worms.

Cause of Allergic Reaction
Unfortunately, in spite of extensive investigations in 70% patients, the cause remains unknown. Such patients are known to have Chronic Idiopathic Urticaria.

Treatment of Allergic Reaction
A large variety of drugs can precipitate urticaria but common ones are pain killers (Aspirin) Sulphonomides, Penicillin, and radio contrast media. 80% of known cases of urticaria are precipitated by Aspirin and its derivatives. Acute attacks are treated with adrenaline and steroids. Antihistamines remain the main stay of management in chronic cases. Antihistamines act by blocking histamine receptors on the blood vessels.

Types of anti–histamines The time to use them
Sedative Anti–histamines have an advantage that they are fast acting, whereas non sedative antihistamines are slow acting. Thus, initially one can use an sedative drug and then switch over to a non sedative antihistamines for maintenance. Fortunately, anti-histamines have no adverse effects even on long term use.