Asthma, Eczema and Allergy – LATEX ALLERGY – ON THE INCREASE

Written by Prof. P. C. Potter

Immediate Type I hypersensitivity to latex is on the increase. Since the first case of latex allergy was reported in 1979 ¹ increasing numbers of patients with type I latex allergy have been published in international journals ^{2, 3} and are now being identified in South Africa ⁴. Although immediate hypersensitivity to latex products (eg. gloves) appears to be a fairly “recent” disease, contact dermatitis (Type IV reactions) to latex products have been well known to dermatologists since the 1920’s.

It is now well known that the agents responsible for delayed contact dermatitis in these patients are the accelerators and hardening agents used in glove manufacture and include thiurams, carbamates, mercapto benzothiazoles and phenylene diamines.

PATCH testing diagnoses sensitivity to these reagents. These patients are able to wear rubber gloves, which do not contain the relevant contact allergen. These, gloves are often incorrectly referred to as “hypoallergenic” even although most of the so-called hypo allergenic gloves do contain latex itself. “Hypo allergenic” gloves are typically thiuram or carbamate free.

Latex allergy typically occurs in health care workers who use surgical gloves and examination gloves. Thus, surgeons, theatre sisters, anaesthetists and midwives have a high prevalence of sensitization (between 5.6% – 7.4%) ². Of all the risk groups children with spina bifida or congenital urological disorders have the highest incidence of sensitization, of the order of 30-40% ⁶.

Deaths from latex anaphylaxis reported to the FDA, have particularly resulted from exposure to latex catheters used in barium enemas.

The first pattern is when patients go from being asymptomatic, through a stage of contact dermatitis, progressing on to generalised urticaria and then develop rhinoconjunctivitis, bronchospasm and anaphylaxis.

Another group of patients develop urticaria early and then develop systemic symptoms (eg. bronchospasm) and/or rhinoconjunctivitis.

The 3rd pattern is more sinister as these patients may quite suddenly progress from being asymptomatic to the development of anaphylaxis, or severe bronchospasm, without a cutaneous phase.

Once sensitization has taken place, avoidance of exposure is essential in view of the unpredictable natural history of the disease. Patients with underlying atopy and females have a greater risk of the development of latex allergy.

It is still unclear as to which of the numerous latex proteins are the most important allergens since different groups of patients appear to have specific IgE to different latex proteins. More research is required in this area. Latex extracts and in-vitro tests therefore vary in their quality and quantity of the different allergens and thus the results of studies from different parts of the world are not always comparable.

Although the latex proteins are obvious sensitisers, it should be remembered that other allergenic proteins and substances might also be incorporated into gloves e.g. ethylene oxide, corn starch and casein. Patients have been identified who are sensitive to these, rather than to the latex itself ⁵.

However, sensitization can occur to latex containing products in a non-medical environment: in children the commonest source of exposure occurs when blowing up balloons. Latex containing products include condoms, baby nipples, buretrols, catheters, chewing gum, dental cofferdams, face masks, golf grips, headsets, bathing caps, milking machines, pacifiers, rubber bands, syringes, injection vials, teething rings and tennis grips.

Although all of these products may contain latex, the ability to release free latex proteins is variable. If the product is processed extensively, washed extensively and hardened, free latex proteins are reduced. Gloves are notoriously variable in the amount of free latex. Powdered gloves typically release latex into the air and when these particles become airborne in air conditioning systems they sensitise health care workers. Health care workers may sensitise themselves after removing gloves and touching their mouths or eyes with unwashed hands.

The manufacturing process for good latex gloves should include an extensive washing process to remove soluble latex proteins. Many manufacturers skip or shorten the washing process to improve productivity and are marketing more dangerous and highly sensitising latex gloves at a cheaper price. In general, non-powdered gloves are safer.

The simplest way to confirm sensitization is the CAP-RAST latex test. This can be performed on 0.5 ml clotted blood, holds no risk to the patient, is highly specific and 70-80% sensitive.

If the CAP RAST is negative, in vivo tests may be performed. One of these is a glove usage test. In this test the patient wears 1 finger of the glove for 2 hours and the skin is then inspected for evidence of urticaria (if the skin is the target organ).

If the symptoms are mild the patient may test wear different gloves (latex free, powder free or latex containing) and compare their symptoms. Skin prick testing is 80-95% sensitive and very reliable, but may be dangerous in certain patients. Skin Prick Tests should never be performed in patients who have had anaphylaxis and should always be conducted in a hospital environment.

“In house” skin prick testing can be prepared by placing 2-3 ml saline in the finger of a glove overnight and using the saline latex extract for skin prick testing. Using locally available gloves the sensitivity of such testing is approximately 80%. Commercial skin prick tests are available in Canada and France and should be used with care, since anaphylactic reactions following skin prick tests have been reported.

They should wear a medic alert disc and it should be made clear to them that they are at risk should they undergo hospitalization, surgical procedures or even when visiting a dentist or gynaecologist. They should always carry a supply of a rapidly acting anti histamine (eg. Phenergan tablets), an adrenaline inhaler (EPIHALER) and/or adrenaline syringe (Anaguard or EPIPEN) to use in the event of inadvertent exposure. Their ordinary physician should be informed, as well as their employer.

Patients with documented sensitivity may be eligible for workers compensation and/or medical boarding and need complete evaluation by an occupational health team, which should include an allergist. Their folders should be clearly marked “Latex Allergy”.

These are made by:

• Regent
• Dalhausen (vinyl)
• 4H glove (Lynby Denmark)
• Tactylon (Smart Practice Phoenix)
• Neolon (Deseret Medical Inc)
• Ansel Dermaprene (Ansell, America).

If latex free gloves are not available powdered free gloves with the lowest extractable latex protein should be used (eg. Regent, Biogel). It must be emphasised that the majority of so called hypoallergenic gloves are free of thiurams (the most potent type I sensitiser) and thioureas and although they can be used for patients with type IV hypersensitivity they are not suitable for patients with true latex allergy. For a comprehensive summary of the contents of different gloves the reader is referred to the analysis by Heese et al ⁸.

Only latex free gloves should be used and when patients return to the wards after “latex free” procedures, great care should be taken that inadvertent latex exposure does not take place in the wards either (e.g. catheters etc.).

Hospitals must become more particular about the kind of gloves they choose, to avoid sensitization of their staff, increasing staff morbidity and expensive workers compensation law suits. It is likely that with new technology e.g. molecular biology, new types of synthetic gloves will replace natural latex gloves. Until this new era dawns, it is important that health professions are aware of the risks of latex allergy to themselves and their patients. Appropriate measures taken timeously will avoid exposure and unnecessary sensitization.