Latex Allergy
Recently, latex products have become ubiquitous in our environment. Latex is particularly prevalent in the medical realm; many medical devices and gloves are made from latex. Its popularity can be attributed to properties of strength, elasticity, tear resistance and superior barrier qualities. Despite these attributes, latex has recently become the focus of a serious health problem for healthcare workers and patients alike: latex allergy.
Even though contact dermatitis caused by rubber and latex has been understood for years, it is believed that numerous cases of latex allergy go unrecognized and uninvestigated. The earliest North American reports of latex allergy were published in 1989. Between 1988 and 1992 the Food and Drug Administration (FDA) received more than 1,100 reports describing allergic or anaphylactic reactions to latex, including 15 deaths. The dramatic increase in reported reactions to latex is believed to result from one or a number of interwoven factors. The adoption of universal precaution protocols in 1987 precipitated a large increase in the use of latex products. Prior to that time, 800 million latex gloves were used per year. As the fear of contracting HIV and other viruses from blood and other body secretions increased, the use of gloves soared to 10 billion gloves per year. The resultant increase in the use and demand for latex products, particularly gloves, greatly escalated. American manufacturers could not meet supply needs quickly enough, leading to a huge influx of foreign-made gloves and changes in the process of glove production to speed manufacturing processes.
The use of cornstarch powder as a lubricant and donning aide is a major contributor to the problem of latex allergy. The powder acts as a carrier for latex proteins contained in the gloves. This powder-antigen complex is released into the atmosphere when an individual puts on or removes latex gloves. The powder-antigen complex can be inhaled by anyone within range and can also enter open wounds and sensitize an individual.
Processing and Manufacturing
Latex is a sap obtained from the rubber tree Hevea brasiliensis. More than 2,000 plant species actually produce forms of latex, but Hevea brasiliensis is the best for commercial use. Ninety percent of harvested rubber is used in the manufacture of extruded rubber products, injection molded goods, and tires for vehicles. The other 10% is used in the manufacture of dipped products such as balloons, gloves, and condoms. Dipped products are thought to be primarily responsible for the anaphylactic responses to latex.
Once the sap of Hevea brasiliensis is collected, ammonia is often added to serve as a preservative and another agent is supplied to prevent autocoagulation. Secondary preservatives such as zinc oxide and sodium pentachlorophenate are also added when low amounts of ammonia are used. This mixture is centrifuged to create an ammonia latex concentrate which is then sold to manufacturers of latex products. Manufacturers add to the liquid latex concentrate other chemicals to serve as additional preservatives or to change the physical properties of the latex. The manufacturers then heat the latex in the presence of sulfur to improve the elasticity and thermostability of the rubber. Latex that has undergone this process is called vulcanized rubber. Concentrated liquid latex is used in the production of dipped products. In the dipping process porcelain molds are coated with a coagulating salt such as calcium alginate and then dipped into the vulcanized latex concentrate.
Clinical Presentation
The manifestations of latex allergy are variable, ranging from mild contact urticaria to a severe anaphylactoid reaction. Thus, it is important for the pharmacist and other healthcare professionals to become familiar with the clinical manifestations of latex allergy. Two main classifications of latex allergy are Type VI and Type I reactions.
Type VI delayed hypersensitivity is the most common allergic reaction to latex. Allergic contact dermatitis is the defining feature, characterized initially by itching, redness and vesicles, and later by dry skin, fissures and sores that tend to be confined to the area of contact. In healthcare workers this reaction usually involves the hands. The delayed hypersensitivity is an acquired immune reaction mediated by Langerhan’s cells, T-lymphocytes, and various lymphokines. Langerhan’s cells process and present the antigen to the T-cells in the skin. These reactions typically occur 4–6 hours after exposure and peak within 24–48 hours. Allergic contact dermatitis can be classified as acute, chronic, or subchronic. In chronic contact dermatitis the skin can become reddened, thickened, lichenified and either hypo- or hyperpigmented.
Type I reactions are IgE-mediated and usually occur within 20–60 minutes of exposure to the antigen. The clinical manifestations of a Type I reaction depend on the individual’s susceptibility to the antigen and the conditions of the exposure. Mild Type I reactions appear to be cutaneous, ranging from localized urticaria to nonspecific burning and itching. Symptoms can progress to a severe generalized urticaria or to systemic involvement. Gastrointestinal symptoms of nausea, vomiting and abdominal cramping can occur with Type I latex allergy. Finally, if the respiratory or cardiac system is involved, a Type I reaction can manifest as angioedema, conjunctivitis, rhinitis, asthma, hypotension and anaphylaxis. Life-threatening anaphylactic reactions have often been associated with mucosal exposure to latex or with tissue and peritoneal exposure to surgical latex gloves during surgery. The clinical manifestations of Type I reactions result from mast cell degranulation releasing histamines and other mediators following the cross-linkage of IgE molecules by latex proteins on the surface of mast cells. The prevalence of Type I latex allergy in the general population is unknown.
The search for why different latex allergy reactions occur is still inconclusive. The major latex allergens have been difficult to characterize for many reasons. First, IgE from latex-sensitized individuals reacts with different protein components. This supports the theory that more than one allergen is responsible for latex sensitivity. Also, chemical processing and heating are thought to contribute to the generation of new allergenic epitopes during the manufacturing process. The range of allergen content in various latex products is great; the difference can be 400-fold in different brands of disposable gloves. The sheer number of possible allergens contributes to the difficulty of determining which are responsible for latex allergy. Currently it is believed that the antigenicity of latex stems from two types of antigens: chemical additives and natural proteins found in latex.
Two Types of Antigens
The two types of antigens can lead to the two types of clinical manifestations. Type VI reactions are thought to be caused by chemicals added in the manufacturing process versus natural proteins found in the latex. As many as 200 different chemicals may be present in latex products; however, accelerators and antioxidants such as thiurams, carbamates and mercaptobenzothiazoles are considered the primary allergens responsible for Type VI reactions. The additional chemicals added are manufacturer-specific. Type I reactions are believed to be caused by proteins in the latex itself and not by added chemicals. Depending on the manufacturing process, latex may contain water-soluble, heat- and chemically stable protein moieties which vary in size and antigenic properties. A variable amount of protein antigens can be removed by washing or leaching during the manufacturing process. However, even this process does not remove all natural latex proteins that can possibly cause a reaction. A variety of proteins have been found in latex products. The high number of antigens may also derive from different plant sources and storage techniques. Another factor that hampers identification of allergens responsible for latex allergy is the possible existence of “invisible” antigens. “Invisible” antigens may be present in various latex products and formulations but are undetectable by the current assays used to find potential antigens. Further research is needed to identify the major and minor latex allergens, isolate the most common ones to develop better diagnostic methods, and control the allergenicity of latex products.
The incidence of latex allergy is unknown due to underreporting and lack of education in this area. Some sources have suggested that its prevalence in the general population is less than 1%, and 1 out of 800 in preoperative patients. Among healthcare workers the general prevalence of latex allergy is 7%–10%, increasing to 24% in those with atopic allergy. Anyone can become sensitized to latex, especially those who frequently wear latex gloves. Although the exact incidence is unknown, latex allergy generally occurs in well-defined risk groups, e.g., healthcare workers, rubber industry workers, and children with spina bifida and urogential abnormalities. Other contributing factors also might lead to the development of a latex allergy. A history of atopy such as atopic dermatitis, rhinitis, or asthma may correlate with the propensity to develop latex allergy. A documented allergy to certain fruits (see TABLE 1) has been associated with the occurrence of latex allergy.
Table 1. Foods That Can Cross-React with a Latex-Sensitive Patient
| Apples
Avocados Bananas Carrots Celery Cherries Chestnuts |
Hazelnuts
Kiwis Melons Papayas Peaches Pears |
Pineapples
Potatoes Rye Strawberries Tomatoes Wheat |
This association has been attributed to the existence of common allergens found in both the fruit and latex. However, this cross-reactivity is not seen in all latex-sensitive patients, and vice versa. At the present time it is unclear if the fruit-sensitive patients may be an independent risk group. Peaches, figs, passion fruit, papayas, chestnuts, celery, avocados, and bananas have produced immediate or anaphylactic-type reactions in patients with latex sensitivity.
Diagnosis is a Challenge
Diagnosing latex allergy is an extensive and uncertain task.
Clinical History: The first step and best method of diagnosis is to obtain a complete clinical history and to identify patients at risk. The healthcare professional should include questions regarding rashes after contact with latex gloves, itching in the vaginal or rectal area after the use of condoms or diaphragms, and any swelling or itching after dental exams or blowing up balloons. The presence of spinal bifida, urogenital abnormalities or any other medical condition requiring multiple surgeries is also relevant. Questions about exposure to latex products on the job are also relevant, especially for persons who work in the rubber industry. Last, the interviewer should inquire about any atopic conditions the person has, such as asthma, food allergies, etc.6 Allergic reactions of unknown cause should be evaluated and discussed thoroughly. However, even the most thorough history will not identify all patients with a latex allergy.
Once a tentative diagnosis of latex allergy has been made based on the history or clinical evidence, it must be decided if further testing should be done in order to obtain a more definitive diagnosis. Several testing methods are available. These include skin testing, epicutaneous testing and latex-specific IgE testing.
Skin Testing: Skin testing is performed with extracts derived from various means, such as soaking latex gloves in diluent solutions. One drawback of this method is that the type as well as the amount of antigens in latex gloves made by different manufacturers is highly variable and can even vary from lot to lot.
Therefore, the most reliable extract is one derived by the same product that caused the reaction. Extracts of ammoniated latex is another source for skin testing. This source could be more helpful since dipped products derived from ammoniated latex are the most suspected source in latex allergy. The possibility of other antigens being added by vulcanization does exist, however. Two less frequently used and less useful products available for skin testing are nonammoniated latex and Hevea leaves.
Epicutaneous Testing: While epicutaneous testing is an option for latex allergy testing, it carries significant risk. The occurrence of anaphylactic reactions to this type of testing is high, and these events have occurred without regard for risk group or history of anaphylaxis. At this time there is no FDA-approved skin test for latex allergy.
Immunoassay Testing: Immunoassay testing involves the in vitro measurement of specific IgE that binds latex proteins. Variables that can affect the results of these types of tests are patient population, source of latex antigen and the assay used.
A positive immunoassay test result to latex in the presence of a suggestive latex allergy history is useful and may be used to avoid the risk associated with the other types of tests. Approved commercial immunoassays are available in the U.S.
Treatment
There is currently no long-term treatment for latex allergy. The best way to prevent future occurrences is for the patient to avoid latex exposure. Unfortunately, many household and medical items contain latex, and not all of these are obvious. TABLES 2 and 3 show a sample of these products. Latex-free therapeutics and supplies are listed in TABLES 4 and 5. If total avoidance is not possible, certain tips can help minimize the risk.
Table 2. Recommendations for the Latex-Sensitive Patient
| • Wear a medical alert bracelet.
• Tell all healthcare providers — e.g., pharmacists, dentists, nurses, physicians — of your allergy to latex. (Never count on the information to be in your records.) • Obtain a list of natural rubber-containing products. • Carry non-latex (vinyl or neoprene) gloves for emergencies. • Carry auto-injectable epinephrine and a beta-agonist inhaler with you at all times as an emergency kit. • Remember that “hypoallergenic” does not mean latex-free.
|
Table 3. Sources of Latex in the Hospital Environment
| Adhesive strips
Balloon catheters Bed protectors Blood pressure cuffs Bulb syringes Casts Catheters, indwelling, condom, rectal pressure Cold packs/hot packs Colostomy pouches Dental dams Dental bite blocks Elastic wraps, e.g., ACE bandages Enemas Endoscopes G-tubes Gloves Medication vial stoppers NG tubes OR masks, hats and shoe covers Peak flow meters Spacers for MDI inhalers Syringes, all types Tape, e.g., first aid Tourniquets Wound care products |
Table 4. Selected Latex-Free Products by Manufacturer
| Glaxo
Cefuroxime 1.5 g (Zinacef) Add-Vantage vials Cefuroxime 750 mg (Zinacef) Add-Vantage vials Lederle Acetazolamide (Diamox parenteral) 500 mg/vial Clindamycin phosphate 150 mg/mL 2 mL, 4 mL, 6 mL, and 10 mL vials Minocycline (Minocin) IV 100 mg/vial Piperacillin sodium (Pipracil IV/IM), all presentations Piperacillin and tazobactam sodium Zosyn IV, all presentations Lilly Ceftazidime (Tazidime) 1 g Add-Vantage vials Cefuroxime (Kefurox) 1.5 g Add-Vantage vials Cefuroxime (Kefurox) 750 mg Add-Vantage vials Merck Hydrocortone Acetate injection Hydrocortone Phosphate injection Measles, Mumps and Rubella Vaccines, Live (M-M-R)Measles (Rubeola) Virus Vaccine, Live, Attenuated (ATTENUVAX) Mumps Virus Vaccine, Live (MUMPSVAX) Phytonadione (AquaMEPHYTON) Rubella and Mumps Virus Vaccine, Live (BIAVAX) Rubella Virus Vaccine, Live (MERUVAX) Varicella Virus Vaccine (VARIVAX) Pfizer Azithromycin (Zithromax) for injection 500 mg vial Fluconazole (Diflucan) in sodium chloride diluent 200 mg/100 mL and 400 mg/200 mL in Viaflex Plus plastic containers Fluconazole (Diflucan) in dextrose diluent 200 mg/100 mL and 400 mg/200 mL in Viaflex Plus plastic containers Pharmacia & Upjohn Clindamycin (Cleocin) 600 mg and 900 mg Add-Vantage vials, 300 mg, 600 Depo estradiol sterile solution vials 5 mg/mL, 5 mL vials Dexrazoxane (Zinecard) injection and companion sodium lactate diluent 250 mg and 500 mg Estring vaginal ring Hydrocortisone (Solu-Cortef) sterile powder ACT-O-VIAL 40 mg, 125 mg, Hydrocortisone (Solu-Cortef) sterile powder 100 mg vial Tolbutamide (Orinase) diagnostic sterile powder 1 g vial Roche Ceftriaxone (Rocephin) 1 g Add-Vantage vials Ceftriaxone (Rocephin) 2 g Add-Vantage vials Schering-Plough Albuterol, USP (Proventil) inhalation aerosol Albuterol sulfate, USP (Proventil HFA) inhalation aerosol Albuterol sulfate, USP (Proventil) inhalation solution 0.083% Albuterol sulfate, USP (Proventil) Solution for inhalation 0.5% |
Beclomethasone dipropionate, USP (Vancenase) Pockethaler nasal inhaler
Beclomethasone dipropionate, 42 mcg (Vanceril 42 mcg) Inhalation aerosol Beclomethasone dipropionate, 84 mcg (Vanceril 84 mcg double strength) inhalation aerosol Celestone Phosphate Injection USP Celestone Soluspan Injectable suspension, USP 6 mg per mL Interferon alfa-2b recombinant (Intron A) for injection vials Labetalol hydrochloride, USP (Normodyne) injection, multi-dose vials Nitroglycerin (Nitro-Dur) Transdermal Infusion System SmithKline Beecham Cimetidine (Tagamet) single dose premixed plastic container Granisetron (Kytril) Hepatitis A Vaccine (Havrix) Hepatitis B Vaccine (Engerix-B) Ticarcillin and clavulanate potassium (Timentin 3.1 g) Add-Vantage vials Wyeth-Ayerst Bicillin C-R Injection Tubex Bicillin L-A Injection Tubex Bretylium Tosylate Injection vial Diazepam injection, USP vial, syringes and cartridge Epinephrine injection, USP Tubex Gentamicin Sulfate injection vial and cartridge Hydromorphone HCl injection, USP vial, Tubex and Blunt Pointe Meperidine HCl injection, USP Tubex and Blunt Pointe Morphine PCA Vial Oxytocin injection, USP Tubex Phenergan injection Tubex and Blunt Pointe Phenytoin Sodium injection, USP vial Procainamide HCl injection, USP vial Sodium nitroprusside, USP vial SMX/TMP Concentrate for injection, USP vial Thiamine HCl injection, USP Tubex Water for injection, bacteriostatic, USP Tubex Zeneca Atenolol (Tenormin) IV injection 10 mL vial Cefotetan (Cefotan) 1 g and 2 g Add-Vantage vials Cefotetan (Cefotan) vials all strengths Chlorhexidine gluconate (Hibiclens/Hibistat) all sizes Meropenem for injection (Merrem) all vial sizes and Add-Vantage vials Propofol (Diprivan) All ampules, vials, prefilled syringes, vent spikes, and stop cocks |
Table 5. Latex-Free Pharmaceutical Supplies*
| • Pharmacy trays | • 5 cc syringes |
| • Allergy syringes | • 10 cc syringes |
| • TB syringes | • 20 cc syringes |
| • Insulin syringes | • 30 cc syringes |
| • 3 cc syringes | • 60 cc syringes |
*All products listed are available from Terumo Medical Corporation.
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