It is an eruption or itching wheal usually of systemic origin.It may be due to state of hypersensitivity to foods or drugs,foci of infections,physical agents(heat,cold,light and friction),or psychic stimuli.
It occurs in hypersensitive or allergic persons.Constitutional treatment is essential.

Symptoms/Problems Remedy Frequency(doses)
After taking rich,fatty food,meat etc.,better in open,cold air;loss of thirst Pulsatilla 30 or200 3 hourly
After taking tinned food,acid fruits,ice cream,over ripen fruits,better by heat Arsenic alb.30 or 200 3 hourly
After taking strawberries Oxalic acid.30 3 hourly
After taking mushrooms Absinthium 30 3 hourly
With severe burning and swelling;after taking crabs;no thirst;frequent urination Urtica urens Q or 30 3 hourly
After taking spoiled fish carbo veg.30 or 200 3 hourly
After taking milk Sepia 30 or 200 3 hourly
After taking aspirin,anacin,etc. Antipyrin 30 3 hourly
After taking Quinine;excessive salt or after suppression of Malaria Natrum mur.30 or 200 3 hourly
After mosquito bites;better washing with icy cold water Ledum pal.30 or 200 3 hourly
After undressing;cold weather;better by warmth Rumex 30 or 200 3 hourly
Due to change of weather;exposure to cold wet weather;violent itching while undressing Dulcamara 30 or 200 4 hourly
Sudden;after exposure to cold,dry wind with anxiety Aconite nap.30 or 200 2 hourly
After bathing;itching on getting warm,disturbing sleep Bovista 30 2 hourly
Every spring;better by heat.Throwing of the clothes aggravates Rhus tox.30 or 200 3 hourly
With sudden severe swelling amd burning;worse by heat;loss of thirst Apis mel.30 or 200 3 hourly
In the beginning of winter;filthy smell from the body even after bath Psorinum 200 or 1M 10 min(3)
Due to gastric catarrh;tongue thickly whitish coated;worse by heat Antimonium crud.200 10 min(3)
Chronic urticaria;rashes on whole body with itching Astacus fl.30 3 hourly
After taking alcoholic drinks;chilly patient;feels better in warmth Nux vomica 30 or 200 3 hourly
Urticaria without itching Uva ursi Q or 30 4 hourly
Due to suppression of intermittent fever Elaterium 30 3 hourly
Urticarial rash with burning;fever;worse by heat,wearing woolen clothes;better by cold Hygrophila spinosa 30 4 hourly