ADHA - Infection Control

In the modern dental office, the delivery of oral health care is made efficient and safe by the use of numerous devices, materials and products. Each of these items in the office armamentarium has a specific use and/or function essential to the dental procedure. Most importantly, each has a formulation of ingredients and/or chemicals that allow the item to perform its function. Impression materials, acrylic and composite dental materials, etching agents, disinfectants, gloves and other products containing natural rubber latex (NRL) and a myriad of other products, when properly handled, are remarkably safe to use in the dental office. However, almost anything can induce an allergic reaction in a sensitized individual and to a small but ever-increasing segment of health care workers (HCWS) and the general population. Exposure to allergens, especially NRL, can precipitate life-threatening reactions; furthermore, individuals exposed to the many chemicals that abound in the dental environment may experience a variety of adverse reactions. Both the health care provider and the patient are potentially at risk. This article will review allergy and related issues in the dental office, with emphasis on those associated with NRL.

The human immune system is a remarkable network of cells, tissues and organs that defend the body against infection from bacteria, parasites, fungi, viruses and other invaders. However, in certain individuals, the normally beneficial immune response acts inappropriately. For example, the immune system, for a variety of reasons, can mistakenly identify the body’s own cells or tissues as foreign and mount an attack (autoimmune disorders).[1-3] In other instances, normally harmless foreign substances such as pollens, dust mites, mold spores food, latex, insect venom, medications (drugs) and other allergens/antigens can cause an individual to experience an exaggerated pathological immune response.[1-4] This phenomenon is known as allergy.

Upon exposure, the immune system mistakenly recognizes a particular allergen/antigen as an invader and generates large amounts of the antibody immunoglobulin E (IgE). The IgE attaches tightly to the body’s mast cells and basophils and is specific for that one particular antigen.[1-4] When reintroduced, the antigen attaches to the specific IgE antibody (like a key fitting into a lock) releasing inflammatory mediators, such as histamine, which initiates the allergic reaction.[1-4] Reactions range from very benign to life-threatening and can occur from exposure of a sensitized individual to almost anything. During the initial immune response, the allergen/antigen, known as the sensitizing dose, is broken down into smaller peptides by antigen presenting cells.[1-4] These peptides are then presented to T cells, which secrete cytokines that induce B cells to produce antigen-specific IgE. The allergic individual is now sensitized to that particular antigen, and subsequent exposure will result in an allergic reaction.[1-4]

The number of exposures to an allergen required before sensitization occurs is highly variable. Some individuals are easily sensitized with a single exposure, but others may have multiple, and in some instances prolonged contact before sensitization.[1-4] Once a person is sensitized, the subsequent exposure to that allergen/antigen, which is known as the challenge dose, results in cross-linking of the IgE antibody bound to the mast cells and basophils, causing the release of histamine and the initiation of an allergic reaction.[1-4] The severity of symptoms is extremely variable and dependent on numerous factors, including the extent of sensitization.[1-4] In some instances, the reaction is very limited; in others, very severe. Due to the tremendous range in the clinical presentation, accurately diagnosing the allergy and identifying the allergen that initialized the allergic response can be very difficult.

Prevalence of Allergy

An estimated 40 to 50 million Americans suffer from allergic diseases.[1-4] The costs associated with allergic disease are estimated at $7.9 billion/year, of which $4.5 billion was spent on direct medical care and $3.4 billion represented lost work productivity.[1-4] In the USA, allergic rhinitis may affect as many as 40 million people, and an estimated 35 million Americans suffer from upper respiratory tract symptoms that are allergic reactions to airborne allergens.[1-4] Eleven million Americans suffer with asthma, a condition often provoked by airborne allergens.[1-4] The prevalence of allergic diseases such as allergic rhinitis and atopic dermatitis has risen substantially in recent decades as a result of higher levels of pollution of the water and air.[1-4] Food allergy is a becoming a major public health concern in the USA, affecting more than 12 million Americans, and is the leading cause of anaphylaxis outside the hospital, resulting in 100 to 200 deaths per year.[5-8] While any type of food product can cause an allergic reaction, 90 percent of cases result from eight foods: milk, egg, peanut, tree nut, fish, shellfish, soy and wheat.[5-8] Other products derived from food and/or plant proteins can be allergenic. Among the most problematic is latex.

Latex Issues

Allergy to Natural Rubber Latex

Natural rubber latex (NRL), the primary component of most gloves used in health care, is collected as a milky, viscous liquid from the tree Hevea brasiliensis. While a superb material for gloves and other products, latex is highly allergenic.[9-11,14] Very complex in its composition, an estimated 50 or 60 different proteins in NRL may provoke the allergic response.[9-11,14] Allergy to NRL is known as a type I or immediate hypersensitivity (Table I).[9,11,14] Because this reaction is an immune response mediated by circulating anti-NRL antibodies, it can develop within minutes; hence, the designation “immediate.” [9-11,14] Type I allergic reactions can be variable in severity, from minor itching and a rash to anaphylaxis and death.[9-11,14]

The exact prevalence of latex allergy is unknown and varies greatly based on the overall exposure of an individual to NRL, the study population and how the data was collected. FDA began to collect reports of adverse reactions during medical procedures and subsequently identified NRL allergy as an emerging public health concern, ultimately identifying over 1,000 allergic and anaphylactic reaction reports associated with use of NRL.[2] In the summer of 1997, FDA issued a medical alert to raise clinicians’ awareness about NRL.[12]

The first documented allergy to NRL in the dental profession was reported in 1987.[13,14] During a routine gynecological exam, a 39-year old dentist experienced an anaphylactic reaction to an unknown allergen, later identified as NRL.[13,14] Based on the most recent data, the National Institute of Occupational Safety and Health (NIOSH) reports that one percent to six percent of the general population may be sensitive to NRL.[10,14-19] The prevalence in HCWs seems to be higher than the general population. From a high in the 1990s of 12 percent to 17 percent, the prevalence of NRL allergy in regularly exposed HCWs sensitized to latex has fallen to 8 percent to 12 percent.[10,14-21] The decrease in the prevalence among HCWs is attributable to alerts and recommendations by regulatory agencies such as FDA, NIOSH and CDC; manufacturing changes in rubber products; increased worker awareness; more familiarity of physicians with latex allergy and improved methods for diagnosing it.[14,22,23] Factors for the increased level of latex allergies reported in HCWs include:

Non-HCWs who had occupational exposure to latex had prevalence reported as high as 11 percent, almost twice as high as the general population, suggesting that the more exposure to NRL, the higher the risk for developing allergy to NRL.[10]

In order to make NRL a workable material, numerous chemicals must be added, including vulcanizing agents, accelerators, activators, blockers, retarders, anti-oxidants, preservatives, odorants, colorants, stabilizers and processing aids.[9-11,14] This porridge of chemicals can cause contact dermatitis. Although allergy to NRL has been recognized since the early 1990s, contact dermatitis to rubber gloves used in surgery was reported by Downing in 1933.[26]

There are two forms of contact dermatitis (allergic and contact) associated with the use of products containing NRL (Table I).[9-11,14,27-28] Allergic contact dermatitis (ACD), also referred to as delayed hypersensitivity or sometimes chemical sensitivity dermatitis, is an immune system-mediated type IV (delayed) allergy that occurs when an allergen, usually chemical additives contained in latex products, interacts with sensitized T lymphocytes located in the dermis and epidermis.[9-11,14,27-28] Type 4 reactions take hours to days to appear (delayed hypersensitivity), usually within 48-96 hours after exposure, and are limited to the area contacted by the materials containing the chemicals.[9-11,14,27-28] The exposed skin presents with an acute dermatitis that may become dry, crusted and thickened, with vesicle formation common.[9-11,14,27-28]

In contrast, irritant contact dermatitis (ICD) is a nonspecific reaction that is not mediated by the immune system and is not a true allergic reaction (Table I). Sufferers present with a rash characterized by hand erythema, dryness, cracking, scaling and vesicle formation, very similar to ACD.[9-11,14,27-28] A number of factors play a role in the development of ICD, including chemical exposure, repeated hand washing and drying, incomplete hand drying, use of cleaners and sanitizers, exposure to powders added to the gloves, sweating or rubbing under the glove, and residual soaps and detergents.[9-11,14,27-28] Because the clinical presentation of allergy to NRL, ACD and ICD can be similar, especially upon the first presentation, anyone who has symptoms consistent with exposure to NRL should be referred for medical evaluation.

Diagnosis of Latex Allergy

An accurate diagnosis is essential. One should suspect latex sensitivity in anyone who presents with any of the following symptoms after exposure to NRL:

Any patient who experiences any of these symptoms should be referred for medical evaluation.[10,11,14,24,27-28] All HCWs should report any symptoms to their immediate supervisor and should also be evaluated by a physician. As additional exposure to NRL can have catastrophic consequences, appropriate referral should be made as soon as possible. A final diagnosis will be made by evaluating the data from the medical history, physical examination and laboratory tests that detect circulating antibodies to NRL proteins.[10,11,14,28] The most reliable test is the skin prick testing (SPT) with a standardized source of NRL. Although easy to perform, rapid and highly sensitive, SPTs are not approved by FDA and are not readily available in the USA.[10,11,14,28] Consequently, many physicians prefer to use serologic (blood) tests, which are not as sensitive as SPT and have higher rates of false negatives (25%) and false positives (15%).[10,11,14,28] Testing for ACD utilizes an FDA-approved test (Patch Testing) where special patches containing latex additives and standardized chemical allergens are applied to the skin for 36 - 48 hours, then removed and the skin examined at 30 minutes, and one, two and five days after patch removal.[10,11,14,28] A positive reaction is shown by itching, redness, swelling or blistering where the patch covered the skin.[10,11,14,28] Dental workers should advise their physicians to test them with the standard series of contact allergens and dental-specific contact allergens, which include glutaraldehyde, methacrylates, amalgam, mercury, palladium, gold, eugenol and benzoyl peroxide.[14] The diagnosis of ICD is made when the health history and symptoms of the HCW are consistent with ICD and patch testing for ACD, and allergy to NRL protein results are negative.[14] The individual who experiences ICD, ACD or latex allergy may have to seek the services of both an allergist and a dermatologist. Final diagnosis can take a considerable period of time, but is essential for a favorable resolution of the condition.[14]

Management of NRL Allergy, ACD or ICD

Identification, education and avoidance are the cornerstones to management of NRL allergy, ACD or ICD. There are literally thousands of consumer and health care products that contain NRL.[10-11,14,24,27-28] A partial list of the most commonly encountered items is found in Table II.[10-11,14,28] Individuals who have increased exposure to products containing NRL have higher prevalence of latex allergy than the general population. The major risk groups are listed in Table III.[10-11,14,24,27-28] Additionally, as NRL proteins are derived from a plant (tree), there is a degree of cross-reactivity with other plant proteins that are similar.10-11,14,24,27-28 Therefore, people who are allergic to banana, kiwi fruit, chestnut, avocado, tomato, potato and papaya are at risk for developing latex sensitivity.10-11,14,24,27-28 Others at high risk are the elderly and persons who present with multiple allergies.10-11,27 Once identified, those who are allergic or at high risk can be educated on what to avoid and how to avoid it to minimize their contact with NRL.10-11,14, 27-28

Health Care Workers with NRL Allergy, ACD or ICD

Because of the universal adaptation of standard precautions into dental practice, clinicians who perform invasive procedures, which include almost all dental practitioners, have an increased exposure to NRL. Latex gloves became the standard in the early 1990s and are still preferred due to fit, sensitivity, effectiveness and relatively low cost. All HCWs who exhibit any symptoms consistent with NRL allergy, ACD or ICD should be evaluated by a qualified physician as soon as possible to obtain an accurate diagnosis.[10-11,14,24,27-28] Once the problem is diagnosed, avoidance measures can be instituted. A list of steps that should be followed to protect allergic HCWs from latex exposure and allergic reactions in the workplace are listed in Table IV.[24,27] In latex-sensitive HCWs, contact with NRL proteins in all forms (Table II) should be avoided, and the overall latex profile for the entire office should be reduced as much as possible.[10,11,14,24,27-28] Allergic practitioners should use only nonlatex gloves (nitrile or vinyl) and other staff members in the dental practice should wear either nonlatex or reduced protein, powder-free latex gloves.[10-11,14,24,27-28] The use of powder-free latex gloves is recommended since the powder in the glove becomes impregnated with the latex proteins.[10-11,14,24,27-28] When powdered gloves are put on or removed, particles of latex protein powder can become aerosolized, exposing dental providers and patients to aerosolized NRL proteins.[10-11,14,24,27-28] Sensitization can occur by this route, and allergic reactions can develop in both HCWs and patients. Therefore, powder-free products, including gloves and rubber dams, are recommended whenever latex-sensitive individuals are in the area.[10-11,14,24,27-28] The overall latex exposure can be further reduced by using reduced-protein, powder-free latex gloves for the other non-latex sensitive clinicians/staff in the office. Further reduction measures include the following: frequently changing ventilation filters and vacuum bags used in latex contaminated areas, checking ventilation systems to ensure they provide adequate fresh or recirculating air and cleaning all work areas contaminated with latex dust.[10-11,14,24,27-28] In addition to NRL, HCWs can develop ACD or ICD from any of the myriad of chemicals used in manufacturing, processing and curing of NRL products, as well as to metals, acrylics, disinfectants and/or other materials/products/ chemicals used in the dental office. Most importantly, everyone on the dental staff must learn about the signs and symptoms of latex allergy and how the risk of exposure to NRL proteins can be minimized. It is advisable that any allergic individuals obtain and wear an appropriate medical alert bracelet.

In order to reduce adverse latex reactions, FDA has issued a rule requiring labeling statements on medical devices, including device packaging, that contain NRL, stating, “Caution: This Product Contains Natural Rubber Latex Which May Cause Allergic Reactions.”[29] Furthermore, as hypoallergenic gloves do contain NRL, effective September 30, 1998, the claim of hypoallergenicity had to be removed from the labeling of medical devices that contain NRL.[29] OSHA requires employers to ”furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.” [30] This would include provision of latex-free alternatives to NRL sensitive employees.

Management of the Latex Sensitive Patient

As with HCWs, latex-sensitive patients should not have direct contact with latex-containing materials (Table II)[10-11,14,24,27-28] Dental treatment should be performed in, as much as possible, a “latex-safe” environment.10-11,14,24,27-28 A thorough medical history is essential to identify latex-sensitive patients and those at risk for developing latex sensitivity (Table III)[10-11,14,24,27-28] The medical history will help detect other allergens that may cause ACD or ICD. Considerations in providing safe treatment for patients with possible or documented latex allergy are listed in Table V.[24,27] Prior planning is essential to developing a “latex safe” environment. The armamentarium and supply inventory must be carefully scrutinized to identify any dental products/materials such as prophy cups, rubber dams and orthodontic elastics. These should be eliminated or replaced with non-latex substitutes in the latex-free setups.[24,27] Nitrile, vinyl or other latex-free gloves should be used in anyone with a known latex allergy.[24,27] Prudence would dictate using latex-free gloves and materials on those at high risk for developing latex allergy (Table III), even in the absence of previous allergenic symptoms. Clinicians must be prepared to respond to medical emergencies.[24,27] While anaphylaxis is very uncommon, it does occur. Having a well-stocked medical emergency kit that contains essential emergency drugs, and having a readily available source of oxygen and a system to ventilate a patient, are essential. All staff members should be trained to summon emergency medical response, and regular drills should be conducted to reinforce these skills.

Conclusions

Louis G. DePaola, DDS, MS, is a professor in the Department of Diagnostic Sciences and Pathology, Dental School, University of Maryland, Baltimore. He received his DDS in 1975, completed a master’s degree in oral biology, is a diplomate of the American Board of Oral Medicine and the American College of Dentists and has a certificate in prosthodontics. He is an international lecturer and executive director, Biosafety and Continuous Quality Improvement, Dental School, University of Maryland Baltimore. Active in research, he has authored and co-authored of over 130 journal articles, book chapters and abstracts and serves as a consultant to the American Dental Association and numerous other professional groups and private industry.

Jacquelyn L. Fried, RDH, MS, received her Bachelor of Arts degree in political science and her Certificate in Dental Hygiene from the Ohio State University. She also holds a Master of Science in Dental Hygiene from Old Dominion University. She is associate professor and director of the Dental Hygiene Program in the Department of Health Promotion and Policy at the University of Maryland Dental School. She has been in dental hygiene education for almost 30 years. She has been involved with clinical, research, didactic and community activities related to tobacco. She currently serves as principal investigator for a tobacco training grant funded by the State of Maryland. An active member of the American Dental Hygienists’ Association, Fried is widely published and has authored numerous manuscripts and book chapters. She teaches both didactically and clinically and has received student awards for her teaching abilities.

This article and the accompanying online survey are sponsored by an educational grant from Crosstex International.

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Introduction