Urticaria is a raised itchy skin rash due to exposure to an allergen, sometimes called a “nettle rash” or hives. Acute urticaria is a fast reaction, often caused by food, insect sting, or medications, and can last between several hours and several days.

Common causes of acute urticaria:

• Food : shellfish, nuts, egg and dairy products
• Medication : antibiotics (penicillin, tetracycline, sulphonamides and cephalosporins), blood pressure pills (ACE inhibitors and diuretics), codeine and aspirin containing pain killers
• Bee and wasp stings

The underlying physiology of urticaria is stimulation of the mast cells in the subcutaneous tissue. They secret chemicals called histamines when stimulated, which will cause the blood vessels to dilate, and fluid is expelled from the blood vessels to the surrounding tissue with the swellings seen. Other chemicals will stimulate the nerves with an intense itchy feeling.

Signs

Most people know what hives look like. When it is due to insect bites, there are some isolated discrete “itchy bumps”. Medication and food taken internally will have a much wider distribution on different parts of the body, and may have different shapes. Some people will have swellings in the lips, eye areas, or the whole face. When it is so severe to involve the tongue or the pharynx, suffocation may occur and results in death.

Typical Urticaria

Treatments

Mild cases such as insect bites require only some anti-itch cream such as menthol, with or without oral anti-histamines. They will resolve after a while if scratching is avoided. Slightly worse cases may need to apply steroid cream.

Those caused by food and medication internally usually are more severe, and will need oral anti-histamines or steroid to control the symptoms. The most severe cases require injections of anti-histamines or steroid for a fast result.

The older generation of anti-histamines include Chlorpheniramine、Diphenhydramine and Hydroxyzine. They all cause some drowsiness and affect driving and work. It is best to take them before bed. The usually anti-histamine injected by the doctor is Chlorpheniramine.

The newer generation is more effective, and has the advantage of not causing drowsiness. There are Loratidine, Cetirizine and Fexofenadine. They only have oral preparation.

The response to different anti-histamine is different. If it is not too satisfactory with one of them, then it is reasonably to try another one, sometimes with dramatically improvement. It is also not uncommon to use more than one anti-histamine to achieve a better control.

However, all these only control the symptoms. It is only when our body system gets rid of all the allergen inside, then the urticaria will stop.