What's that weird rash?

Urticaria sounds a bit ominous doesn't it? In most cases it's not. Urticaria is a rash, which is triggered from some kind of allergic reaction. Sometimes called 'weal's' they can appear for what you think may be for no reason. The allergy could be from something you have had before, but for some reason, your body does not like the idea of it and decides to have a reaction to it. On the other hand, it may be from something you've never consumed before, so you had no idea that you were allergic to it.

The rash usually looks like an irregular shaped red mark, they often come up where you have been scatching, and the mark or marks remains, it may become white or yellow with a red rim a little later on. The rash may then come and remain for several hours with or without itching and stinging.

So what's it from?

Urticaria can arise from an allergic reaction from one of many things; some of these include:
Foods such as milk, shellfish, eggs, nuts, strawberries, yeast
Additives or preservatives in certain foods
Drugs such as penicillin, aspirin, or opiates (codeine, morphine, pethidine)
Other cases may be from stings from vegetation such as nettle
Temperature extremes

So what causes the red marks to appear?

If you become allergic to something, the allergy causes your immune system to respond. The thing you are allergic to is called an allergen. When you are allergic to something your immune system makes the antibody called IgE. IgE is responsible for histamine production. You may have heard of the drugs called 'antihistamines' these often help to counteract the attack. Histamine is released into the lower layer under the skin and causes the blood vessels to dilate (get bigger); therefore there is more blood under the skin's lower vessels. The pressure in these vessels causes fluid to leak out into the surrounding tissue, causing it to swell into a rash.

Who is most susceptible?

There are a select few that are more susceptible to urticaria. They are those who suffer from asthma, eczema, or hayfever. This is because many of these people are predisposed to suffering from a skin reaction. This can be due to the fact that these conditions are related to the release of the antibody IgE.

If you have never had this kind of rash before, it's important to identify the cause of it. For some this can be easy, it may be that every time they eat eggs for example, they come out in this rash. Unfortunately it may not be that easy for some.

If you cannot work out the trigger, it is helpful to keep a food, drink and drug diary, along with when you get the symptoms. If you are to do this it is a good idea to speak to your doctor first before you tackle this on your own. Sometimes your reaction to the unknown allergen may be more severe the next time, and if you start to get other reactions, such as swelling in the tongue or throat, you will need to go to hospital immediately.

Another way to test for the allergen is to get a skin-patch test. If you are going to have this test done it is a good idea to narrow down what may be causing the allergy. This should be done in conjunction with your doctor. A skin patch test is where a small amount of the 'suspected allergen' is placed upon your skin and tested to see if a small rash appears. If a rash does appear to one of the tests, you have your culprit.


For most people the rash will come and go within the first few hours of being in contact with the allergen. If this is the case, aloe vera or calamine lotion may help to soothe the itching. If this does not work, over the counter antihistamines should help, however these should not be the solution to the allergy. Antihistamines usually have side effects, such as drowsiness, and should not really be used long term. It is also important that if you discover the allergen, and it is related to a drug, that you inform your doctor so that he /she knows not to prescribe you that specific drug in the future. If you suffer from urticaria, I wish you happy hunting when it comes to finding your allergen, but please do it under your doctor's supervision.

- Louise Ganey