What urticaria is
Wheals form when cells in the skin called mast cells release histamine and other chemicals, causing fluid to leak into the skin. Each wheal typically lasts less than 24 hours and disappears without a mark, while new ones appear elsewhere. Angioedema is the same process in the deeper layers of the skin, causing swelling of the lips, eyelids, hands, feet or genitals that lasts longer and may be painful rather than itchy. About half of people with urticaria have both.
Acute versus chronic
Acute urticaria lasts less than six weeks. It is common, especially in children, and is often triggered by a viral infection, a medication, a food or an insect sting. Frequently no cause is found and it resolves on its own.
Chronic urticaria means hives on most days for more than six weeks. In most cases, called chronic spontaneous urticaria, no external trigger exists; the condition is driven by the immune system itself, sometimes with an autoimmune component. Chronic inducible urticaria is set off by a physical stimulus such as pressure, cold, heat, sunlight, exercise or firm stroking of the skin. Chronic urticaria typically lasts one to five years and eventually resolves in most people.
Common triggers and aggravating factors
- Viral and other infections, the most common trigger in children
- Medications, notably certain painkillers of the anti-inflammatory class, some antibiotics, and blood pressure medicines of the ACE inhibitor class for angioedema
- Foods and food additives in acute cases, far less often in chronic urticaria
- Insect stings
- Physical stimuli: pressure, cold, heat, sunlight, vibration, exercise
- Stress, alcohol and overheating, which worsen but do not cause chronic urticaria
When it is an emergency
Swelling of the tongue or throat, difficulty breathing or swallowing, a hoarse voice, wheeze, chest tightness, faintness or collapse alongside hives may indicate anaphylaxis. Call 911 or go to the nearest emergency department immediately. Do not wait for a clinic appointment. Anyone who has had such a reaction should be assessed for an adrenaline auto injector and, where a trigger is suspected, referred to an allergist.
Assessment at DermCare
The diagnosis is made from the history and, where wheals are present, the examination. Images of the rash taken at home are very helpful because wheals may have faded by the time of the visit. Your dermatologist asks how long individual wheals last, whether there is angioedema, what medications you take, any pattern with physical triggers, and whether there are symptoms such as fever, joint pain or weight loss. Extensive allergy testing is not helpful in chronic spontaneous urticaria and is not routinely done. Limited blood tests may be arranged. A skin biopsy is taken only when wheals last longer than 24 hours, bruise or are painful, to exclude urticarial vasculitis.
Treatment options
Avoid what can be avoided
Identified triggers and aggravating medications are stopped or substituted where possible. Cooling the skin and wearing loose clothing reduce itch.
Antihistamines, stepwise
Modern non sedating antihistamines taken regularly every day, not just when hives appear, are the first line for all forms of urticaria. If standard dosing does not control symptoms within two to four weeks, the dose is increased in steps up to four times the standard dose, which is safe and recommended in current guidelines. Older sedating antihistamines are avoided because of drowsiness and poorer effectiveness.
Second line options
For chronic urticaria not controlled by high dose antihistamines, an injectable biologic therapy that targets the antibody involved in the allergic pathway is approved in Canada and is effective for most patients, given monthly. Alternatives include an oral immunomodulating medicine used under monitoring, and in some cases a leukotriene receptor antagonist added to antihistamines. Short courses of oral corticosteroids may be used to break a severe flare, but are not a long term treatment because of their side effects.
For referring physicians
Please refer patients with urticaria persisting beyond six weeks despite regular non sedating antihistamines at up to four times standard dose, patients with recurrent angioedema without wheals, and any patient in whom individual lesions last more than 24 hours, leave bruising, or are accompanied by fever, arthralgia or other systemic features. Include the duration, current antihistamine and dose, all other medications with a note on ACE inhibitors and anti-inflammatory use, and images where available. Patients with a history suggesting anaphylaxis should be referred to an allergist in parallel. How to refer.