Latex allergy has become an important health concern in recent years especially in the occupational setting with health care workers. The adoption of universal precautions in infection control has promoted the widespread use of latex barrier products. This has been associated with an increase in the diagnosis of latex allergy as well as awareness of the extent of this problem. While specific treatment is not available, awareness of the problem and avoidance in sensitised individuals are important cornerstones of management.
Definition of latex allergy
As with other types of immediate type hypersensitivity, the diagnosis of latex allergy requires both a history of symptoms on exposure to latex and the demonstration of latex-specific IgE (either by skin prick or in-vitro tests). Either criteria alone is insufficient to diagnose latex allergy.(Figure 1).
What are specific latex allergens?
Natural rubber latex is derived from the rubber tree, Hevea brasiliensis, with the basic unit being a low molecular weight compound, cis-1,4-isoprene. Native latex coagulates by forming polymers of isoprene several thousand units in length, and is coated with a layer of protein, lipid and phospholipid which provides structural integrity. Proteins comprise only about 2% of the total content of raw latex, but are the source of allergens causing clinical reactions. A number of latex protein allergens have now identified, with different allergens being important in the different risk groups. The functional roles of these proteins in the native rubber plant are unclear, but some of these may function as enzymes.
Who is susceptible to latex allergy?
The prevalence of latex allergy in the general population is low, and estimated to be less than 1%. However, there are certain distinct groups who have an increased risk for latex allergy. These include health care workers, children with spina bifida, and rubber workers.
The prevalence of latex allergy in patients with spina bifida is between 24% to 60%, and among health care workers, the reported prevalence is between 5% and 15%.
Health care workers at particular risk are those with frequent use of latex gloves or products, such as operating theatre, intensive care or dental staff.
What are the factors promoting sensitisation to latex?
In all risk groups, the likelihood of sensitisation increases as exposure to latex increases. Hence, health care workers at the beginning of their training have the same likelihood of latex allergy as the general population, but the likelihood of developing latex allergy increases as with time in the profession. Similarly, in children with spina bifida, the prevalence of latex allergy is directly related to the number of surgical procedures they have had. Conversely, there appears to be no increased risk associated with age or sex. Atopy has been found to be a risk factor for health care workers in some studies, but not in children with spina bifida.
How does sensitisation occur?
Latex exposure can occur through direct contact with the skin, mucosal surfaces (such as eyes, nose and airways, oral cavity or the genitourinary tract), or parenterally (such as intravenously, or intraoperatively). Latex allergens appear readily able to cross skin and mucosal surfaces on direct contact to initiate the sensitisation process.
Cornstarch glove powder has an important role in the sensitisation process. Latex allergens can be leached from rubber gloves by normal skin moisture and be adsorbed to cornstarch powder within gloves. They can also be directly adsorbed to powder in gloves which have not been worn. When gloves are donned or removed, the latex-allergen coated cornstarch particles become aerosolised, and are a source of respiratory sensitisation and triggering of attacks.
What are the symptoms of latex allergy?
The typical symptoms of latex allergy are related to IgE-mediated mast cell release of inflammatory mediators. Initial symptoms include irritation on contact with itching, redness and swelling. Typically, these symptoms occur within minutes on skin contact with latex gloves, or other rubber products. As exposure and sensitivity increases, the severity of symptoms increases and may include contact urticaria and spread to adjacent areas of skin. Up to 6-8% of these individuals may have serious generalised systemic reactions with latex exposure. Contact of skin with latex or oral, vaginal, or rectal exposure also results in the development of localised allergic manifestations, which may progress to generalised reactions.
Airborne exposure, particularly to aerosolised latex allergen laden cornstarch from powdered latex gloves may lead to nasal, ocular and respiratory symptoms. Ocular symptoms may begin with conjunctival itching, tearing, chemosis and oedema. Nasal symptoms include sneezing, watery rhinorrhoea and congestion. Respiratory symptoms range from throat irritation and cough to life-threatening asthma. Gastrointestinal, cardiovascular and genitourinary symptoms have also been well documented. Although severe systemic reactions have occurred after cutaneous and respiratory exposure, direct mucosal and parenteral exposure poses the greatest risk of anaphylaxis. While uncommon, latex induced anaphylaxis is the most severe manifestation, and fatalities have been reported.
There is an association between latex allergy and allergy to a variety of fruits, including banana, avocado, potato, tomato, chestnut and kiwi fruit, probably because latex protein allergens are structurally homologous with other plant proteins. Latex allergic patients may describe oropharyngeal itching and swelling when eating some of these fruits.
How to diagnose latex allergy?
As with all aspects of allergy, the foundation of diagnosis is a careful and detailed clinical history. Important elements of the history include timing and duration of latex exposure; the relationship of exposure to the onset of symptoms; the types of symptoms, including any suggestion of a systemic reaction, and the progression of symptoms over time.
Other history which may be helpful in supporting the diagnosis include a background history of atopic disorders such as hayfever, asthma or eczema, and oral reactions to the cross-reacting fruits listed above.
Although the history alone may be strongly suggestive, diagnosis requires confirmatory testing. Worldwide, skin prick testing is the most common method used to diagnose latex allergy. A commercial extract is available for skin prick testing, but is not registered by the Therapeutic Goods Administration. Systemic reactions are also more frequent with latex skin prick tests than for aeroallergens. Hence, latex skin prick testing is recommended only in specialist or hospital clinics with appropriate resuscitation facilities. In vitro blood tests are also commercially available for latex specific serum IgE. These are less sensitive than skin tests, but are not associated with provoking systemic reactions. They are the diagnostic tests of first choice if there is a history of anaphylaxis.
Patients with a strong history of allergic reactions and negative skin or in-vitro tests may need a challenge test (such as a glove donning test) to further clarify the diagnosis. As with latex skin prick tests, these should only be done in specialist or hospital clinics. A negative test in this case may allow the worker to return to the work place.
What is the treatment of latex allergy?
To date, avoidance of latex products is the only means of preventing serious reactions in allergic individuals. There are some reports of successful desensitisation immunotherapy, but this remains an investigational form of treatment, and avoidance is the mainstay of therapy.
In health care workers with only mild symptoms, the use of non-powdered latex gloves may reduce the frequency or severity of symptoms, but non-latex alternatives are preferable.
In more severely allergic patients, total avoidance is necessary, including preventive measures such as wearing a medical identification bracelet. Surgical procedures should only be carried out in latex-free operating theatres. Being prepared for inadvertent exposure by carrying antihistamine and oral steroid tablets, and possibly an adrenaline autoinjector (EpiPen or Anapen), is also an important aspect of management.
The widespread use of non-powdered latex gloves in health care settings significantly reduces the acquisition of latex allergy in health care workers and should be widely advocated.
References and further reading
- Poley GE, Slater JE. Latex allergy. J Allergy Clinical Immunology 2000;105:1054-62
- Kurup VP, Fink JN. The spectrum of immunologic sensitization in latex allergy. Allergy 2001; 56:2-12
© ASCIA 2010
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Content updated January 2010