Urticaria and angioedema
One person in 5 will suffer from these conditions over the course of their lifetime, and often in a variable fashion. Sometimes it is because of a true allergic reaction, triggered by a food, a medication, an insect sting, exposure to a chemical product, or another sensitizer such as latex.
However, most commonly, urticaria is not allergic in nature. Consequently, it should be no surprise that the allergist will frequently not suggest allergy skin tests.
Urticaria is a disease characterized by the development of raised welts or hives, angioedema (swelling) or both at once. Hives or urticaria are localized itchy and swollen plaques of variable size; lesions are fleeting, last less than 24 hours in the same spot, and don't leave a trace. When the swelling involves deeper tissues, we speak of "angioedema".
This should be differentiated from other conditions since raised plaques, angioedema, or both can sometimes be symptoms of other diseases.
Classification of urticaria and angioedema
- Urticaria and angioedema
- Acute (lasting less than 6 weeks)
- Allergic (food, medication, insect, contact)
- Infectious (viral, bacterial, parasitic)
- Idiopathic (no cause identified : many cases are likely viral in origin)
- Chronic (lasting more than 6 weeks)
- Spontaneous : 90%
- Auto-immune 40%
- Idiopathic (of unknown cause) 50%
- Inducible : 10%
- Physical urticarias
- from cold, from heat
- from the sun
- from delayed pressure
- Other types of urticaria
- triggered by physical exertion
- Conditions that may involve urticaria
- Systemic inflammatory diseases
- Angioedema mediated by bradykinin (without urticaria)
Clinical presentation of different forms of urticaria
Acute urticaria is the most frequent form of urticaria. A food allergy or an insect sting, or a reaction to an NSAID (non-steroidal anti-inflammatory medication) can lead to an acute form, lasting several hours to a day, and sometimes associated with symptoms other than on the skin such as rhinitis and/or asthma, digestive trouble (nausea, vomiting, diarrhea, cramps), a fall in blood pressure or convulsions: this is known as anaphylaxis. When it lasts longer, we think of medication allergy or an urticaria associated with a viremia. Frequently, no evidence of a trigger can be found.
Chronic spontaneous urticaria is an urticaria that lasts more than six weeks. The intensity of the lesions, their frequency and the degree of itching is very variable from one patient to another, and can fluctuate in the same patient. About 40% of these cases are attributable to an auto-immune phenomenon, and 50% are unexplained to date. The long term evolution is also very variable from one patient to another, lasting several months to several years, often with intervening periods of limited disease activity.
Inducible urticaria (representing approximately 10% of chronic spontaneous urticaria) can be triggered by a physical stimulus, such as local pressure (dermographism and delayed-pressure urticaria), cold, heat, the sun, vibration, and water. There are other forms of inducible urticaria: cholinergic urticaria, which is triggered by heat, emotion, exercise and finally a form of urticaria uniquely triggered by physical exercise alone, or exercise in association with another contributing factor (a food, a medication).
Different conditions that may involve urticaria
Anaphylaxis is a severe form of hypersensibility and is very often associated with urticaria and angioedema. Urticaria in an anaphylactic reaction is acute, developing rapidly following exposure to a potential trigger.
Mastocytosis is a disease of mastocytes, the cells responsible for urticaria and angioedema.
Systemic inflammatory diseases (auto-immune, such as lupus, vasculitis, and auto-inflammatory) are associated with other manifestations such as arthritis, photosensbility, Raynaud's syndrome and organ specific disease (kidneys, liver, lungs...).
Angioedema mediated by bradykinin (without urticaria)
Finally there are forms of angioedema without urticaria, mediated by bradykinin, and not histamine, that usually appear slowly (over several hours), that evolve over several days, and which can affect the digestive tract; they don't usually respond to treatments usually given for urticaria mediated by histamine, such as antihistamines (anti-H1), steroids, or even adrenaline given to treat laryngeal edema.
They are often secondary to certain medications, such as ACE inhibitors (angiotensin converting enzyme inhibitors), ARB's (angiotensin receptor blockers), or to alteplase (utilized in thrombolysis).
Less frequently, they are due to a deficit in a factor of complement, the C1 esterase inhibitor, a deficit that may be genetic or acquired; there are also rare cases of hereditary forms not linked to a deficit in C1 esterase inhibitor. All of these forms of angioedema are made worse by estrogens (oral contraceptives, menopausal hormones) that should be avoided. These forms of angioedema are better diagnosed and managed by a specialist in allergy and immunology.
Treatment of urticaria
The primary treatment in acute urticaria is to avoid the trigger, if it is known to be an acute allergic or inducible urticaria. In the case of laryngo-pharyngeal angioedema, adrenaline (epinephrine) can be used. Otherwise, second generation antihistamines (non-sedating anti-H1) taken as needed or regularly are the first line pharmacological treatments; if control is not adequate one can increase the dose up to 4 times the recommended dose. Occasionally corticosteroids can be used for short periods.
It is recommended to avoid first-generation antihistamines (anti-H1, diphenhydramine, hydroxyzine, chlorpheniramine, periactin) because of their side effeects such as somnolence (impaired faculties), changes in memorey, dry mucous membranes, and an increased appetite.
Chronic spontaneous urticaria
Here also non-sedating antihistamines taken as needed or regularly are the first step in pharmacological treatment; if control isn't adequate the dose can be increased 4 times above the usual. The majority of patients will respond favourably to these treatments.
One tries as much as possible to avoid treatment with corticosteroids because of numerous side effects. The addition of montelukast can sometimes help control urticaria that has been difficult to treat on high doses of antihistamines.
If there is little success with these treatments, then a more specialized treatment approach may be necessary, with the addition of omalizumab (a biologic agent), which is often successful in cases of refractory urticaria. Finally, if necessary, immunosuppressants can be used, such as cyclosporine in particular, or others.
It is necessary to identify the stimulus and avoid it; antihistamines can also offer a level of protection in cases of continual exposure to the trigger in question.
Other forms of urticaria and angioedema
These must be distinguished from other forms of acute and chronic spontaneous urticaria, in order to treat them correctly. Their treatment varies depending on the disease in question.
André Caron, MD FRCPC, allergologue et immunologue
translation: Andrew Moore, MD FRCPC
This is an update of the previous version written by Dr Guérin Dorval and Dr John Weisnagel (photos urticaria/dermographism).