The underlying mechanism is essentially the same as acute urticaria, but we do not know what trigger the mast cells to release those chemicals, including histamines, in chronic urticaria. Hence the diagnosis is often called Chronic Idiopathic Urticaria.
What we do know now is that, it is a disorder of the immune system, which somehow produces “auto-antibodies” which in turn attack specific mast cells in our skin and tissues causing an enormous release of histamines. Why we suddenly switch-on production of these aggressive antibodies to attack our own skin cells is still not understood.
Over 50% of chronic urticaria cases are due to production of these “auto-antibodies”, some of them have co-existing auto-immune problems such as thyroid and joint diseases. Most sufferers are younger females, who have twice as much chance of having this as the male counterparts.
Other factors may play a role but are never really confirmed. Food additives, such as salicylate, sodium benzoate, sulphites, colourings and nitrites; chronic undetected dental, urinary or parasitic infections are thought about. Stress is known to aggravate urticaria and stress reduction measures may help.
Definition Of Chronic Urticaria
In general, almost every day in a six week period, there are wide spread urticarial lesions, each of them will not last for more than 24 hours and leaves no trace after disappearing.
Signs
There are itchy lumps of different sizes, at different places, come and go at different time, and last for a different period of time. 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.
Dermatographism
Some physical factors can trigger chronic urticaria, 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 and sweating provoke cholinergic urticaria with tiny swellings around the follicles.
Management & Treatments
Although they are not the actual cause, it is still important to avoid any obvious triggers or exacerbating factors.
- Keep the skin cool, avoid getting hot from exercise and take lukewarm baths.
- Resist the temptation to rub the itchy skin
- Avoid alcoholic drinks
- Avoid foods containing additives
- Avoid medication containing aspirin and codeine
- Avoid too tight clothings
Although it does not make the urticaria go away, 1% menthol in aqueous cream help to soothe the affected skin and reduce scratching, which will make the urticaria worse.
The mainstay of treatment is anti-histamines, which may be necessary for prolonged periods, sometimes many months. Usually the second generation is more effective and they do not cause drowsiness. Cetirizine, loratadine, acrivastine, fexofenadine, desloratadine and levocetirizine are all very useful.
The first generation anti-histamines such as chlorpheniramine, diphenhydramine and hydroxyzine cause drowsiness and it is better to take them before bedtime. Chlorphenamine and loratadine are safe to use in pregnancy, while cetirizine and loratadine are safe to take whilst breastfeeding.
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.
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.
Short courses of oral steroids may be necessary for short periods to settle more severe symptoms. It should not be used for prolonged periods of time as this may lead to stunted growth in children and osteoporosis in adults.
Although as mentioned, some people may have co-existing auto-immune problems, but the vast majority of cases do not have any hidden diseases, and blood tests in general are all un-productive.
Chronic urticaria will resolve on their own in about half of the cases, but many of them will have this troublesome problem lasting for many years.