#AskID - Hives

We asked Prof Niki Ralph:
“Hives, also known as Urticaria, come from the common European stinging nettle, as when one is stung by a nettle, the rash that is seen is also called “nettle rash” and it is a group of raised, pale lesions with surrounding redness associated with itch. The individual lesions are called weals and they appear as isolated areas, or start to spread into multiple joining lesions which may be round or form ring shapes. The pale skin swelling with surrounding redness may last from minutes to hours, then new lesions occur at different sites on the body.
Hives are due to chemical mediators released from mast cells found in the skin. The mediators include histamine, cytokines and platelet activating factor and they cause dilation of the blood vessels, activation of sensory nerves and leakage of fluid into the surrounding tissues, hence the skin appears swollen and red.

Hives/Urticaria may also be associated with angioedema which is a deeper swelling within the skin/mucous membranes (affecting lips/tongue/throat). This is a more serious condition as can lead to difficulty breathing if the tongue and throat swell.
Urticaria is divided into 2 main types:– Acute lasting <6 weeks or Chronic > 6 weeks.
Chronic idiopathic urticaria means there is no identifiable trigger however for some people their flares of urticaria may be induced.
Inducible urticaria includes:
Cold urticaria
Cholinergic (triggered by exercise/sweating)
Pressure urticaria (often seen at sites of tight clothing – waistband, socks, straps)
Aquagenic urticaria (triggered by water)
Solar urticaria (triggered by UV light)
And there are many other more rare types of urticaria

Chronic spontaneous urticaria affects 0.5-2% of the population therefore it is very common. It occurs more commonly in those who have atopic dermatitis (eczema) and also is seen more frequently in women (2/3rd are women). The cause is often not found however it may be triggered by heat, viral infection, tight clothing, medications.
Acute urticaria may be triggered by infection such as a viral infection, bacterial infection (dental abscess/sinusitis); drug -induced such as antibiotics, aspirin, opiates, nonsteroidal anti-inflammatories, contrast dye during a CT scan; bee/wasp sting, or contact due to latex for example.
The diagnosis is usually made clinically and rarely is a skin biopsy required.
Treatment of urticaria may be required for months-years for those suffering with chronic idiopathic urticaria.
They include:
▫️2nd generation non-sedating antihistamines - the doses may have to increase until all symptoms have settled. One may also require taking 2 different types of antihistamine if one alone doesn’t control the symptoms
▫️Avoidance of triggers is important – avoiding trigger medications, tight clothing, heat etc.
▫️Low salicylate diet if one feels it may be triggered by food
If antihistamines alone do not control symptoms Mast cell stabilisers (medication) may be added
▫️Systemic immunosuppressive medications/infusions
▫️Oral steroids/IV steroids may be used in acute emergency setting if one has angioedema however they are not recommended longterm to control urticaria due to their side effects if taken longterm.
Although the majority of patients suffering with chronic urticaria settle, up to 15% of patients may still suffer with wealing twice weekly beyond 2 years