More often known as hives or nettle rash, urticaria is a very common skin condition which affects one in five people at some time in their lives. Women are particularly prone, perhaps because of hormonal influences. With ‘ordinary’ urticaria, weals – intensely itchy raised marks on the surface of the skin – suddenly develop. They are usually short-lived, lasting for a few hours or days, but may last longer. The weals can be any size, appear anywhere on the sufferer’s body and may be numerous. They are usually pale in the middle and red around the edges and are due to dilation of the capillaries – small blood vessels under the skin – which makes their walls more permeable and enables clear fluid called serum to leak out. If enough serum leaks out, blisters may form.
If deeper tissues are involved, a more severe type of urticaria known as angio-oedema may occur. Then the swellings are much larger, commonly affecting the face, eyelids, hands, forearms and throat and sometimes causing serious breathing difficulties. Joints in the arms and legs may also become inflamed and painful. About half the people who suffer from ordinary urticaria have recurrent attacks of angio-oedema too.
So what causes this reaction in the blood vessels? Often it is due to an increased circulation of histamine – a chemical normally present in the body. This increase can be triggered by many factors, including various foods, drugs and inhalants such as pollens, house dust and animal ‘dander’ – skin flakes which the animal sheds naturally and various chemicals which its body gives off. Two foods that are frequently responsible are shellfish and strawberries – so urticaria is a hazard of summer for those susceptible. Other foods that may produce the reaction include eggs, nuts, chocolate, tomatoes, pork, milk and yeast. Artificial colourings and preservatives can do so, too.
Aspirin can also be a cause of urticaria, or it can aggravate it. Penicillin is another possible culprit, as are the nonsteroidal anti-inflammatory drugs often given to treat arthritis.
Sometimes contact with certain substances will bring the symptoms on – cosmetics are one example. Insect stings can also cause this type of reaction, which may even be life-threatening if the breathing is affected .
People whose urticaria occurs in response to triggers such as these are often but not always allergy-prone individuals – sufferers from hay fever, asthma or eczema for example -and the tendency can run in families. Anxiety may also play apart.
Other constituents in the body – called catechol amines -can, by irritating the tissues surrounding them, have the same effect on the blood vessels as histamine and almost anything can act as the trigger in this allergic-type of urticaria. I had it once after eating raw fish in a foreign restaurant, for example, but it may also have been due to the monosodium glutamate used as a taste-enhancer.
It can therefore be exceedingly difficult to track down – in order to avoid – the cause if the attacks are recurrent. In fact three out of four people are unable to do so, in spite of persistent detective work.
Some more unusual forms of urticaria have a physical cause. Cold winds or rain, or just immersing the hands or bathing in cold water, can cause weals to appear in susceptible people. If an ice cube on the skin produces a weal, this confirms the diagnosis of ‘cold urticaria’ – the type that’s induced by the cold.
Some people develop weals when exposed to sunlight -’solar urticaria’. Others may suffer from ‘pressure urticaria’ – deep, painful, non-itchy swellings which occur about two hours after some particular pressure on the skin. The hands may swell, for instance, after carrying a heavy shopping bag, or the balls of the feet after spending some time on a ladder.
Another strange form of urticaria is called dermo-graphism, loosely ‘translated’ as skin writing. A mild, stroking pressure – with a fingernail for example – will produce a temporary, raised line with reddened edges. The skin can literally be used as a drawing board.
Fortunately, however, most cases of urticaria tend to resolve themselves in due course, and in the meantime antihistamine tablets prescribed by your doctor or recom-mended by your pharmacist usually relieve the symptoms and keep the condition under control. For mild cases, soothing creams containing antihistamine which stop the effects of histamine on the blood vessels beneath the skin, or creams and lotions containing calamine lotion help calm down any swelling and itching by cooling the skin, especially if these preparations contain menthol, phenol or camphor.
If angio-oedema is severe and breathing becomes difficult, emergency treatment by injection may be necessary to reduce the swelling.
Urticaria can occur as part of some other underlying condition – thyroid disease, for example. So if the cause is not immediately apparent, or you have more than one attack, or are concerned, do consult your doctor. He or she may wish to do blood tests and other investigations or refer you to a skin specialist.
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