Medical Q&As

Skin rash - what could it be?

Both my sister and myself suffer from the following; whenever our skin gets cold we develop a nettle like rash that goes roaring red (like a scald) and then the skin swells. It seems as if we are allergic to the cold. I have heard of one other person with this condition while I was in Australia. Can you please help us as this is becoming unbearable?

This sounds like a condition known as physical urticaria. External physical influences such as exposure to heat, cold, chemicals or certain plants can cause this form of urticaria. The process that is occurring in the skin is similar to nettle rash except for the fact that it is triggered by cold. The rash erupts due to the release of histamine into the skin. Histamine causes redness and itching of the skin and over several minutes can give rise to wheal formation. The condition can be intensely itchy, which encourages the affected person to rub or scratch the skin. Unfortunately this releases further histamine into the skin thereby making the condition worse. Dermatologists refer to this process as a “scratch itch cycle”. In other words you are itchy therefore you scratch, which makes the itch worse and you scratch again and you get more and more itchy and you repeatedly scratch or rub your skin until you are distracted by the intense irritation in your skin. Therefore the first basic rule with this condition is don’t rub or scratch your skin. If you are very uncomfortable apply an anti-itch product such as calamine lotion to the affected areas of skin. Antihistamine tablets can also be very helpful because they block the effects of the histamine that is released into the skin following exposure to cold. Some people are so affected by this form of physical urticaria that they need to take antihistamines on a continuing basis for many months. It would be a good idea to discuss this matter further with your GP.