Haridra Khandam is a very famous and highly effective Ayurvedic medicine for allergy. It is in granules form. Its main ingredient is Haridra-turmeric.
 
Beneficial in: 
Treatment of allergic skin diseases, itching skin diseases. It improves skin quality and complexion. Also useful in pruritis, blisters, fungal skin infections, hives.

Dosage: 
5 – 10 g once or two times a day before or after food, as directed by Ayurvedic doctor.
It is usually given along with warm milk or honey.

Dosage for children below 5 years of age – 1 – 2 grams, once or twice a day, along with a teaspoon of honey or warm water/milk.