Urticaria, Hives and Allergy Rash

Surrey Allergy Clinic

Urticaria (Hives or "Nettle" Rashes)

by Dr Adrian Morris

Urticaria is a raised itchy and painful skin rash sometimes called a “nettle rash” or hives. There are two distinct types of urticaria:

· Acute urticaria is often caused by an allergy to food, insect sting or medication and can last between several hours and six weeks.

· Chronic urticaria is diagnosed if the rash persists for six weeks or longer, the underlying cause is then usually not due to food allergies.

What are the causes?

Acute Urticaria

The most likely cause of Acute Urticaria is an allergy due to exposure to pets, horses, latex rubber, food such as shellfish, nuts, egg and dairy products or bee and wasp stings. Allergies to medication such as antibiotics (penicillin, tetracycline, sulphonamides and cephalosporins), blood pressure pills (ACE inhibitors and diuretics), codeine and aspirin containing pain killers can cause acute urticaria. Sometimes viral infections such as glandular fever and hepatitis B, or bacteria (helicobacter, streptococci), fungal and parasitic infections can trigger urticaria. Allergic reactions to blood products, transfusions, xray contrast and vaccines have also been implicated. Papular urticaria is the medical term for “itchy bumps” or grouped urticarial lesions seen mainly in children and which follow insect bites from midges, fleas and mosquitoes.

Chronic Urticaria

The cause of Chronic Urticaria is much more difficult to identify. The role of true food allergy is hardly ever a significant trigger but food additives such as salicylate, sodium benzoate, sulphites, colourings and nitrites may play a role. We often end up diagnosing Chronic Idiopathic Urticaria. This condition (which can persist for many years) is due to the production of “auto-antibodies” which in turn attack specific Mast Cells in our skin and tissues causing an enormous release of histamine. Why we suddenly switch-on production of these aggressive antibodies to our own skin cells is a complete enigma. Our bodies may continue producing these auto-antibodies for a number of years leading to a great deal of distress and discomfort for the urticaria sufferer. Unfortunately over 50% of Chronic Urticaria cases are due to production of these “auto-antibodies” to the IgE and its receptor on Mast Cells found in the skin; hence there is a possible relationship to underlying thyroid and joint diseases.

Chronic undetected dental, sinus, urinary or parasitic infections as well as ACE inhibitor blood pressure pills may play a role in triggering chronic urticaria. Stress is known to aggravate urticaria and stress reduction measures are very important in treating chronic urticaria.

Chronic urticaria can also be triggered by physical factors such as exposure to environmental heat (prickly heat), intense cold, sunlight, vibration or pressure on the skin (from tight clothing). Very rarely some people react to bath water, this is called “Aquagenic” Urticaria. Exercising after eating certain foods such as wheat, celery and shellfish might provoke delayed urticaria. Many people have very sensitive skin and any friction or rubbing will cause raised red lines to develop. This is called Dermatographism and indicates just how easily they can release histamine in their own skin. A good test for cold urticaria is to hold a block of ice against the skin for 5 minutes and see if an urticaria weal develops after the ice is removed.

Underlying thyroid diseases and autoimmune diseases such as Systemic Lupus and Rheumatoid Arthritis can provoke Chronic Urticaria or even Urticarial Vasculitis (a variant in which the lesions tend not to fluctuate but lead to skin discolouration). Urticarial Vasculitis may be associated with a fever, bone pains and joint swelling (Schnitzler’s Syndrome). Occasionally children with Coeliac Disease may present with urticaria.

Occasionally an inherited deficiency of the C1 Esterase Inhibitor Enzyme leads to a non-itchy form of urticaria called Hereditary or Familial Angioedema. This condition affects mainly females in a family, is associated with sudden swelling of the face and neck which is painful, but there is no rash. These lesions usually last for 2 to 3 days and do not respond well to antihistamine medication. Sufferers characteristically have low levels of the Complement C4 in their bloodstream and respond to medication such as Danazol or Tranexamic acid which prevent angioedema attacks. Isolated angio-oedema without urticaria may also be triggered by aspirin, ibuprofen, epilepsy and blood pressure medications.

What are the symptoms of Urticaria?

This blotchy rash consists of a number of pale raised bumps or wheals surrounded by reddened skin. The rash is extremely itchy and debilitating.

Lesions tend to move about every 24 hours and “migrate” around on the body.

In chronic cases, the intense itchiness will cause sleepless nights and may lead to a depressive illness. Chronic urticaria tends to fluctuate by temporarily settling down and then suddenly relapsing again with co-existent viral illnesses, stress and aspirin containing medication. This chronic pattern may recur for 5 years to 20 years in some cases!

If your urticaria does not disappear after a few weeks, or does not respond to antihistamine medication, and is accompanied by any other health problem, you should go to your doctor. Blood tests may help identify an allergy or underlying immune disorder.

How do we treat urticaria?

Avoid any obvious triggers or exacerbating factors and try these simple measures:

Keep the skin cool, avoid getting hot from exercise and take lukewarm baths. Resist the temptation to rub the itchy skin and apply copious amounts of moisturising creams to reduce dryness and itch. Avoid alcoholic drinks and foods containing additives and pseudoallergens (sodium benzoate, sulphite, colourings and salicylate).

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

Avoid all aspirin or codeine containing medication (including ibuprofen, diclofenac and mefenamic acid). Only use paracetamol as a painkiller.

Avoid ACE inhibitor blood pressure pills (lisinopril, ramipril, enalapril & perindopril), if you are prone to developing urticaria.

Carefully read Side Effects list of any other medication you are currently taking and avoid medicines that are known to trigger urticaria or angioedema.

Pregnancy may specifically aggravate urticaria as Pruritic and Urticarial Papules and Plaques of Pregnancy (PUPPP syndrome).

Stress, overheating, tight clothing and alcohol may aggravate and make urticaria worse.

The mainstay of treatment is high dose (second generation) ANTIHISTAMINE medication which may be necessary for prolonged periods (in excess of 6 weeks). Double conventional doses of these non-sedating antihistamines such as Cetirizine, Loratadine, Acrivastine and Fexofenadine may be needed to get symptom relief. The new "isomers" called desloratadine and levocetirizine don't seen to offer any additional benefit in treating urticaria.

Traditionally we add "stomach-ulcer treatment" medication such as Cimetidine and Ranitidine which are known to also dampen down histamine release. Occasionally we need to add sedating antihistamines such as Chlorphenamine or Hydroxyzine at night to get urticaria control. Newer leukotriene receptor antagonists currently used for asthma such as Montelukast and Zafirlukast have provided some symptom relief in chronic urticaria when used in combination with antihistamines. Oral antidepressant Doxepin is a good antihistamine but may induced drowsiness, while Doxepin cream can soothe the skin. Short courses of oral cortisone or steroids may be necessary for short periods (one to three days) to settle more severe symptoms. Cortisone should not be used for prolonged periods of time as this may lead to stunted growth in children and osteoporosis in adults. Chlorphenamine and Loratadine are safe to use in pregnancy, while Cetirizine and Loratadine are safe to take whilst breastfeeding.

Specialist investigations in Chronic Urticaria may be necessary to exclude other underlying illnesses or to confirm the presence of “auto-antibodies” in the blood stream (“Anti IgE Receptor Autoantibodies" and "Basophil Histamine Release” can be measured). The Autologous Serum Skin Test (ASST) raises a weal on re-injection of the patients serum and is a good indicator of Auto-antibodies.

Highly specialised third line treatments may include Immunosuppressive drugs such as Ciclosporin (autoimmune urticaria), Methotrexate (non-autoimmune urticaria), and Sulphasalazine (Pressure urticaria). Androgen hormones, Thyroxine, Nifedipine and Warfarin have been used with variable efficacy as well. Colchicine and Dapsone are useful in treating Urticarial Vasculitis. If available, Immunoglobulin injections, Plasmaphoresis or the use of novel anti-IgE monoclonal antibodies such as Omalizumab (Xolair) may be necessary. The future holds many exciting new therapeutic modalities including DNA Plasmid Vaccines.

Reference: Powell RJ, du Toit GL, Siddique N et al, BSACI guidelines for the management of chronic urticaria and angio-oedema. Clin Exp Allergy 2007: 37; 631-650.

May 2008

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