Urticaria and angioedema are common health problems. They often occur together (in 40% of cases) but may also occur separately (50% have urticarial alone, while 10% have angioedema alone).
Urticaria is caused by swelling due to blood vessels in the skin. It manifests as intensely itchy ‘wheals’: blanching swollen papules which may be lighter than the normal skin, surrounded by redness around the wheal.
The wheals may vary from a few millimetres to many centimetres in size. Wheals usually do not last for very long, resolving over a few hours and causing no skin discoloration or scarring when it is gone. Angioedema is due to swelling in the deeper tissues of the skin or mucosal membranes. It is usually asymmetrical, non-pitting and is not associated with erythema. It commonly affects the face, lips, hands and feet, genitalia and the tongue. It may be life-threatening if it affects the larynx. It tends to be painful rather than itchy and may take up to 72 hours to resolve.
When angioedema and urticaria occur together, the diagnosis can be considered the same as if it were urticaria alone. On the other hand, angioedema that occurs without urticaria is due to only a very limited number of conditions, including ACE-inhibitor induced angioedema and hereditary angioedema. Isolated angioedema is very dangerous and can cause fatal upper airway obstruction.
Acute urticaria usually lasts for hours to days. Chronic urticaria is defined as urticaria present on most days for over six weeks. Intermittent urticaria occurs infrequently but over a long period of time.
There are many non-allergic causes of urticaria. These include:
- Viral infections
- The ingestion of direct mast cell destabilisers (eg codeine)
- The ingestion of exogenous histamine (in spoiled fish and other foods)
- Physical stimuli causing the chronic inducible urticarias.
Most acute urticarias are due to viral infections. Viral induced urticaria can last for longer than the usual, because the stimulus causing the urticaria is a virus, which is present for at least a few days. To ensure that acute urticaria is not the first manifestation of a severe allergic reaction, assess carefully for any signs or symptoms in any other body systems. If there is concern about airway, cardiac, GIT or other involvement, think about whether this could be the onset of anaphylaxis.
Chronic urticaria is divided into the chronic inducible urticarias and chronic spontaneous urticaria:
- Inducible urticaria: ‘Physical’ urticarias account for about 25%
- Spontaneous: Autoimmunity accounts for 30% to 50% of cases
- Food additives may play a role in a minority.
Various forms of inducible urticaria can be triggered by cold, light touch, pressure and overheating/exercise. Chronic spontaneous urticaria is usually caused by an autoimmune reaction:
- Autoantibodies against IgE receptor or membrane bound IgE can stimulate the high-affinity receptor for IgE (FcεRI) and stimulate chronic histamine release. This is why chronic spontaneous urticaria can be so hard to control, and requires higher than usual doses of antihistamines.
- Thyroid autoantibodies have been found to be significantly elevated in some patients with chronic urticaria.
IMPORTANCE IN THE COMMUNITY
Urticaria is common and has significant impact on quality of life associated with sleep, absenteeism, social interaction, self-esteem and discomfort. There are health care-related costs and many unnecessary investigations and dietary exclusions.
Education and Avoidance Measures
Provide an explanation and information regarding causation and treatment. Information is available from www.allergyfoundation.co.za for medical professionals and their patients. Apply general measures such as avoiding overheating, tight clothing, recognising the role of stress. Patients should avoid foods and beverages that can cause histamine release. Treat with high dose antihistamines, up to four-fold the dose required for rhinitis or mild urticaria.
At this stage, if patient’s symptoms have not resolved, they should be referred to a specialist, as further steps may involve considering assessment for food additive hypersensitivity, an examination and laboratory investigations for systemic diseases, and a skin biopsy.
Isolated angioedema (without urticaria)
It is important to recognise isolated angioedema and assess patients for the possibility of hereditary angioedema. Recurred episodes of swelling, usually asymmetrical, with or without a family history, should prompt a test of complement C4 levels, and C1 inhibitor levels. Another important cause is ACE inhibitors. Reactions to ACE inhibitors can occur soon after starting the medication or even after many years.
If someone with ACE inhibitors has angioedema, the drug should be stopped and replaced with a suitable alternative. The patient should still be assessed for hereditary angioedema, as ACE induced angioedema is much more common in those with the hereditary deficiency of C1 inhibitor function.
Once the patient is diagnosed they should be referred to (or co-managed with) someone with experience in managing this condition.