Hives is the more commonly-known word for urticaria and is an allergic skin rash which is sometimes known as 'nettle rash'. While urticaria are flat, other skin changes might include macules (raised) or papules (fluid/pus filled). Where hives have appeared the skin will become extremely itchy and hot.

There are two main forms of hives, differentiated by how long the rash persists.

• Acute urticaria is most likely caused by an allergy that is relatively a short-term thing, although it can still take some weeks to resolve in some circumstances.

• Chronic urticaria is more long-term, and remissions and relapses often occur.

One point that should be made clear is, if hives appear together with breathing difficulties and/or wheezing, this allergic reaction may indicate anaphylaxis and should receive prompt medical attention.

The Causes

A wide variety of intolerances could cause hives to occur, so the patient needs to independently address each one to see what the trigger may be. The most likely causes of acute urticaria is:

• Allergy to pets, latex or foodstuffs such as nuts and shellfish. Even dairy products could trigger this reaction.

• Bee or wasp stings, together with insect bites.

• Reactions to certain medicines such as allergy to antibiotics and even aspirin.

• Viral infections could also be a trigger, such as Glandular Fever and Hepatitis B.

• Vaccines and blood transfusions are also a consideration.

Chronic urticaria causes can be very difficult to identify and often the cause may never be found. Below is a list of possible causes:

• Hives may appear at any point on the body once the trigger has happened. This may indicate a cause straight away. For example, if the rash appears on the arms or legs, a sun allergy may be responsible. The rash may have appeared underneath a new ring, which could indicate a reaction to a certain metal contained within the ring.

• Blood pressure drugs, infections from certain parasites or stress may be a contributory factor.

• Exposure to heat, cold, sunlight, vibration or even pressure to the skin. Dermatographism may even occur in people with such sensitive skin which means any rubbing will cause raised red lines.

• Chronic medical conditions can also provoke urticaria. Conditions commonly associated with chronic urticaria include thyroid dysfunction, some cancers, and autoimmune dieases such as Lupus. However, chronic urticaria alone should not be considered a sign that an individual has one of these medical conditions.

• An inherited deficiency of the C1 Esterase Inhibitor enzyme could lead to a non-itchy form of hives known as Hereditary Angioedema.

Bodily Defences

So you know what can cause hives to occur, but what actually goes on inside the body to create hives on the skin?

Simple, but gruesome.

Histamines are released into the blood stream to cope with whatever has triggered the reaction. The cells that they come from line the blood vessels. This makes blood vessels 'leaky' which causes fluid to seep out into the surrounding tissues just underneath the ski - this causes the swelling. Unfortunately, in the same layer of skin, nerve endings are found. The 'leaked' fluid irritates the nerve endings, thus causing the itchiness to occur.

Treatment of Hives

There are many common treatments for hives which are listed below, but if the hives appear to be different or are new, then checking with your local GP is always a good option.

• Keep the skin cool, take lukewarm baths and avoid any exercise.

• Apply 1% menthol in aqueous cream to soothe the skin.

• Avoid any medicines containing aspirin.

• Check medicines you are currently taking for side-effects and ask yourself if the symptoms arose since commencing the medication.

• Moisturisers may help, although hypoallergenic options are always better.

• Normal-dose antihistamines are often used short-term for acute hives.

• High-dose antihistamines may be necessary in more recalcitrant cases.

• In the case of severe symptoms, short courses of oral steroids may be prescribed. Both steriods and antihistamines come in topical solutions as well as systemic forms and these topical forms can also be used to treat hives.

• Specialist investigations may be needed in the case of an underlying illness.

Finally, if you are unsure of the cause or are taking any medication which may be triggering the symptoms, a visit to your doctor is recommended.