Medical Research On Latex Aller

(Based on Hazard Information Bulletin, OSHA. 1998.)

1. Irritant dermatitis. Irritant dermatitis is the most frequently observed reaction to latex products, accounting for 80 percent of work-related reactions to latex gloves.2 This type of reaction results from the drying action of the corn starch and/or other irritant chemicals found in gloves and can be exacerbated by the soaps and mechanical irritation required for surgical scrubbing. Irritant dermatitis is not mediated by the immune system and is not a true allergy. However, the resulting deterioration in skin integrity possibly enhances absorption of latex protein allergens and is believed to accelerate the onset of allergic reactions.

2. Type IV delayed hypersensitivity. Type IV delayed hypersensitivity, also called T-cell mediated contact dermatitis, allergic contact dermatitis, and delayed hypersensi-tivity, directly involves the immune system, in contrast to irritant dermatitis. Among the immunologic responses to latex, 84 percent are Type IV.28 This type of reaction is usually a response to the chemical additives used during the manufacturing process, specifically the accelerators, rather than to the latex proteins themselves. The resulting skin reactions are similar to those caused by poison ivy. Like poison ivy, the skin rash usually appears six to 72 hours after initial contact and may progress from a mild dermatitis to oozing skin blisters. It is important to recognize that not all patients with Type IV reactions progress to Type I reactions. However, 79 percent of Type I patients previously had Type IV symptoms.29

3. Type I immediate hypersensitivity. Type I immediate hypersensitivity, also called IgE mediated anaphylactic reaction or anaphylactic reaction, results when an antigen induces the production of an antibody of the immunoglobulin E class. Re-exposure to the inciting antigen triggers a cascade of events, including the release of histamine, arachidonic acid, leukotrienes and prostaglandins.

Reactions usually begin within minutes of exposure. Symptoms can run the entire spectrum from mild (skin redness, hives, itching), to more severe (cough, hoarse voice, chest tightness, runny nose, itchy or swollen eyes), to life-threatening (bronchospasm and shock). Type I reactions from latex exposure have been reported in patients and health care workers and in a variety of clinical settings, including: vaginal deliveries,30 gynecological examinations,31 dental procedures,32 intra-abdominal33 and genitourinary surgery and during the act of donning gloves.34

Routes of Exposure_

Latex exposure can occur as a result of contact with the skin or mucous membranes or by inhalation, ingestion and parenteral injection or wound inoculation. Among health care workers, the most frequent route of exposure to latex allergens is by cutaneous contact and/or inhalation, and the most common source is medical gloves. In the case of cutaneous exposure, the sensitizing antigens of latex penetrate the skin after being solubilized by sweat. A history of eczema or contact dermatitis is associated with a higher incidence of allergy as a result of the disruption of skin integrity. The potential for harmful exposure is further enhanced by the use of powdered gloves, which promote access of the allergen to the circulation.

The cornstarch powder frequently found on the inner surface of the gloves actively binds allergen. This complex is readily aerosolized with frequent glove changes. Within hospitals, the concentration of latex aeroallergens is often highest in operating rooms, where powdered latex gloves are frequently donned and removed.34 The aerosolized powder/allergen complex can become as dense as 1000 ng/m3 air and remain suspended in the air for up to five hours.24

The aerosolized latex allergen is readily inhaled and has been associated with conjunctivitis, rhinitis, cough, hoarse voice, chest tightness and bronchospasm. Baur et al. have demonstrated a direct relationship between the development of allergy-related symptoms in hospital workers and latex allergen concentrations in their work area. Airborne allergens have also been shown to affect individuals who are in the immediate vicinity but not themselves using latex products.36 Replacing high-allergen gloves with powderless low-allergen gloves can reduce ambient allergen levels 10-fold.34

Patients with Type I latex allergy can also develop anaphylactic reactions as a result of exposure to certain foods, including some tropical fruits (see below). In one report, 17 percent of latex allergic patients also had anaphylactic reactions to some of these foods.

Populations at Risk_

The reported prevalence of latex allergy varies greatly depending upon the population studied and the methods used to detect sensitization. As is the case with all allergy-causing substances, the greater the exposure in a population, the greater the number of sensitized individuals. This was well demonstrated by Tarlo et al. in a study of dental students.38 The incidence of positive skin tests to latex increased as a function of the duration of training: 0 percent of year one and two students, 6 percent of year three, and 10 percent of year four students.

There are several populations at increased risk.

1. Patients with a history of multiple surgical procedures. This group includes patients with congenital genitourinary tract anomalies and those with spina bifida. In one study of spina bifida patients, 60 percent were reported to have Type I latex allergy as determined by history, RAST and/or skin prick test, although not all had demonstrated allergic symptoms.39 The two main risk factors for the clinical expression of latex hypersensitivity in this population are frequency of exposure and a prior history of atopy.40 There is accumulating evidence for a genetic predilection to latex sensitivity in children with spina bifida.41'42

2. Health care personnel. Depending upon the methodology of diagnosis, the prevalence of latex sensitivity among health care personnel has been reported from 2.9 percent43 to 17 percent.12 More recent studies of health care personnel usually have reported a higher prevalence of latex sensitivity than older ones. Approximately 70 percent of adverse events to latex reported in the FDA's MedWatch database involve health care workers, and in most cases the medical personnel were patients themselves.44 The American College of Allergy, Asthma and Immunology (ACAAI) has identified latex allergy as "a major occupational health problem." Among health care workers, a his tory of atopy, eczema or hand dermatitis and frequent use of disposable gloves are associated with a greater risk for developing latex allergy.46,47

Current data indicate a prevalence of latex sensitization of 12.5 percent to 15.8 percent among anesthesiologists and nurse anesthetists.14'1 Brown et al. identified predisposing risk factors such as skin symptoms with latex glove use (hives, rash, itching), a history of atopy and a history of allergy to certain fruits (bananas, avocados, kiwis). In contrast to most other studies, duration of exposure to latex gloves, either by age or by years of work as an anesthesiologist, did not increase the risk of sensitization. While 2.4 percent of their study population was sensitized and exhibited symptoms of latex allergy, 10.1 percent was sensitized but manifested no clinical symptoms of Type I hypersensitivity at the time of the study. This latter group was considered to be presymptomatic and have occult disease. The authors concluded that with further avoidance of latex exposure, these presymptomatic but already sensitized individuals can reduce skin reactivity and serum levels of latex-specific IgE and prevent progression to symptomatic disease. Their report also noted that 24 percent of the anesthesiologists and nurse anesthetists studied had irritant or contact dermatitis.

3. Other individuals with occupational exposure such as rubber industry workers and hairdressers. The prevalence of latex allergy is thought to be similar to that of health care workers, although this population has not been studied as extensively.

4. Individuals with a history of atopy, hay fever, rhinitis, asthma or eczema. In a number of reports examining latex allergy in various populations, atopy was one of the significant predisposing risk factors. In a study of latex sensitization in a low-risk pediatric population, Bernardini et al. reported that all the children with latex sensitization were atopic whereas only 29 percent of non-sensitized subjects had positive skin prick responses to environmental or food allergens.48 Liss et al. demonstrated a five-fold increase in positive skin tests among atopic health care workers compared to non-atopic workers.43

5. Individuals with a history of food allergy to tropical fruits (such as avocado, kiwi, banana), chestnuts or stone fruits.49 These plants contain several proteins similar, or in some cases identical, to those found in latex.

6. Individuals with severe hand dermatitis who wear latex gloves. It has been proposed that the dermatitis (contact or allergic) disturbs the integrity of the skin and facilitates absorption of latex allergen.

7. General population. The prevalence of latex allergy in the general population has been reported to range from <1 percent to 6.7 percent. , The latter figure is of particular interest because it was observed in a random sample from an ambulatory surgical practice. Increased risk factors include non-Caucasian race, younger age, a history of food allergies, asthma and/or atopy, spinal cord abnormalities, stated latex allergy and symptoms when exposed to latex. Unfortunately, the specificity and positive predictive value of history alone in a general population is low.

Diagnosis

Warshaw outlined a sequential evaluation for patients with suspected latex sensitivity. 2 (Table 2). His recommendations include a careful medical history and focused

Table 2: Diagnosis of Latex Allergy

Complete History

+ risk factors

+ clinical symptoms and signs suggesting contact dermatitis or urticaria w

Avoid specific additives

or + with immediate symptoms

Radioallergosorbent Test (RAST) [due to low sensitivity of RAST, may go directly to Skin Prick Test (SPT)]

Avoid Natural _j

Rubber Latex

Avoid NRL

SPT, Scratch Chamber and/or Use Test

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