Illustrated: allergy and immunology

Eight cases of allergic or immune reaction.



This unpleasant condition presents with raised wheals that are intensely itchy. It is often described as ‘hives’ and patients will usually understand the comparison to nettle rash. The aetiology is often problematic. It may be allergic or non-allergic. The allergic variety is IgE-mediated, leading to mast cell degranulation and histamine release. This process may also be triggered by non-IgE stimuli. Usual management involves removal of any obvious trigger, followed by high-dose antihistamines. Some patients will also require H2 antagonists such as ranitidine, montelukast and even cyclophosphamide. Corticosteroids are often not particularly effective.

Varicose eczema

This extremely common condition is seen in older patients with longstanding venous problems. These may be obvious varicose veins, but this is not always the case. It may be that the worst veins are not the very tortuous ones that can look very dramatic, but straighter veins with incompetent valves that cause greater hydrostatic pressure, with fluid leaking out of the vessels in the lower legs. Breakdown of the red cells in the tissues leads to the pigmentation. Chronic eczema and ulceration are the biggest problems.

Mosquito bites

Insect bites and stings are a common presentation in the surgery. They usually take the form of itchy spots, often with a relevant history of the patient seeing the insect. They may present with more widespread areas of inflammation, which can be confused with infection. Treatment with an antihistamine is all that is normally required, unless the reaction is much more severe and associated with angioedema. In these cases, it is usually a bee or wasp sting that causes the problem, and referral to immunology is recommended.

Contact dermatitis

This woman underwent surgery for a benign choledochal cyst. Postoperatively, she developed this allergic reaction to the dressing applied to her wound. It is probably the adhesive on the dressing that was responsible. The dressing was removed and a small amount of mild topical steroid helped to settle the reaction. Butterfly strips were applied to give the wound a little extra support – they did not aggravate the patient’s skin.

Periobital eczema

This patient developed eczema around both eyes after using a new eye make-up. That made the diagnosis straightforward, although this condition is often quite difficult to manage in the apparent absence of a cause that can be eliminated from the patient’s environment. Stopping use of the cosmetic, and applying emollient and topical steroid cream, helped the reaction to settle, although it took a short course of oral corticosteroids for the skin to return to normal.

Skin prick testing

This simple, safe technique can be used to confirm certain allergies. It is usually carried out in the outpatients clinic and a small number of potential allergens are tested, along with a negative and positive control to confirm the validity of any results. The technique is often used in investigation of conditions such as rhinoconjunctivitis. The usual numbers of allergens would be eight to 16 and would include house dust mite, grass and tree pollens, animal dander and so on. A positive response is confirmed by a wheal of at least 3mm, and a positive response to the positive control (histamine) at 15 minutes.

Patch testing

For more complicated cases, where the allergen is less clear, patch testing offers the potential to look at much greater numbers of allergens, usually associated with skin manifestations of allergy. These may involve up to 100 substances, including preservatives, metals, perfumes, plants and rubber. The process takes much longer than skin prick testing and requires follow-up visits. The patches are usually left in situ for 48 hours before being assessed.

Infected eczema

This 60-year-old woman was an alcoholic. She had a history of eczema and this area had become considerably worse. It clearly looked infected, and was treated with oral antibiotics and a short course of oral steroids, followed by topical steroids as the skin started to improve.

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