The oral region of the face is unique, with three different epithelial zones: the cutaneous lips, the vermillion and the mucosa of the oral cavity. The skin of the cutaneous vermillion is similar to the rest of the face. There are typical features such as sebaceous glands, sweat glands and hair follicles. However, the vermillion is non-keratinized. Specifically, areas in this region are considered “non-keratinizing” and therefore lack the typical stratum corneum barrier, including the labial mucosa and wet surface of the vermillion, ventral tongue, floor of mouth, soft palate and buccal mucosa. The mucosa of the oral cavity contains saliva with buffering and solvent action. Susceptibility to allergens varies among these regions.
The signs and symptoms of contact dermatitis in the oral cavity are less well defined than that seen with other regions covered in this series. The classic symptomatology of itching and scaling is often absent. Instead, the non-keratinized oral mucosa seems to show a different set of reaction patterns in response to contactants. Lichenoid reactions are a particularly important pattern seen involving the oral mucosa. While oral lichen planus is the prototypical example of this pattern, extrinsic agents like drugs and contactants should not be overlooked as a potential etiology.1 Clinically, there may be white reticular patches, erythema or erosions. The lesions may be asymptomatic or associated with intense burning. The differential diagnosis is broad and often requires a myriad of techniques to finally arrive at the correct diagnosis. A biopsy is typically warranted and helps to rule out things like connective tissue disease and immunobullous disease. Eosinophils seen on histology are helpful in pointing the diagnosis away from lichen planus and favoring an extrinsic driving force such as a drug or contactant.
Historical clues are also extremely helpful in this setting. Recent exposure to dental materials, metals or plastic sources should be considered significant and patch testing initiated. This is particularly important in localized lichenoid dermatitis in close proximity to the suspected oral implant or prosthesis. Areas that should be considered most suggestive for oral contact lichenoid reactions are the lateral tongue and buccal mucosa. These are the areas in closest proximity to amalgams (fillings) and most prosthetic devices.1 Metals used in dentistry are most often mercury, nickel, gold, cobalt, palladium and chromium. Sources of exposure to these metals include dentures, braces, crowns and fillings (amalgams). Other causes of oral lichenoid contact dermatitis include flavorings (with cinnamon being the classic example) and dental adhesives (acrylates).2 Allergy to acrylates from dental prostheses may also cause tingling or jaw pain.3
One other consideration with regard to contact dermatitis affecting the oral cavity is the so-called “burning mouth syndrome” (BMS). While this disorder is likely a localized dysesthesia with both psychological and neurophysiological components, it may be prudent for some patients to undergo patch testing to help exclude contact dermatitis. It has been suggested that patients with a fluctuating course of BMS may represent a subset of patients in which allergic contact dermatitis is relevant. Unfortunately, only a few patch test studies assessing BMS have been done and show mixed results.4,5
Oral hygiene products may cause allergic contact dermatitis in either the mucosa of the oral cavity or on the lips.6-8 Therefore, rashes that involve both the oral cavity and the lips are very suggestive of an allergy to chemicals in mouthwashes, toothpastes, dental floss and chewing gum. In toddlers with skin eruptions in the mucosa of the oral cavity or on the lips, exposure to rubber in pacifiers should also be considered.9,10 The oral mucosa is frequently exposed to food. Food additives and flavorings may cause mucosal inflammation.
The lips are often exposed to cosmetic products. In a recent patch test study published by the North American Contact Dermatitis Group, isolated lip dermatitis was determined to be allergic in 38.3% of patients. The most common allergen source was cosmetics.3,11,12 Allergic contact cheilitis may be the result of allergy to chemicals in lip balms, lipsticks, lip glosses and sunscreens.12,13 The anatomy of lipstick is surprisingly complex. There are dyes, flavoring agents, sunscreens and preservatives in addition to the vehicle.11 A common historic allergen in lip products is castor oil, which is used as a solvent for pigments. Lanolin, another common component in lip products, is used as an emollient and has induced an allergic response in individuals.12 Cases of postoperative patients reacting to Aquaphor Healing Ointment were shown to react specifically with lanolin alcohol.14 Benzophenone, found in many lip products and sunscreens, has also been found to be a common allergen.12 Both allergic contact and allergic photocontact dermatitis may be seen.15 Patients may sometimes decide to use “natural” products, under the impression the products are free of irritants or allergens. This is a popular misconception, as such products may be contaminated with allergens, including bee’s wax and associated propolis (also known as bee glue).16 Assessment for natural product lines such as Burt’s Bees will help the detection of unsuspecting allergens.
Exposure to metal lipstick casings or the habitual sucking of metallic objects (pen or pencil) can also be the cause of isolated allergic contact cheilitis. In these patients, there is often a more focal plaque of chronic dermatitis, which represents the contacted site. Similarly, a focal plaque of chronic dermatitis on the mid-lower lip may be seen in a musician who plays a wind instrument. The allergen may be the mouth piece itself or the wooden reed.12,17
More unique or exotic contactants should also be considered when focal plaques of dermatitis on the lips are encountered. Things like musical instruments, pipes and even blowguns need to be considered.18 See Figures 1 and 2. Anything that contacts the lips needs to be considered, including a significant other or spouse. The transfer of a contactant inadvertently from one person to another (usually a significant other or spouse) has been referred to as consort contact dermatitis. The prototypical vignette is a wife with allergic contact cheilitis driven by an allergy to her husband’s aftershave.19
“Lip licker dermatitis” is an irritant dermatitis that involves the perioral skin.20-22 Clinically, there is usually a hyperpigmented circumferential symmetric plaque that is red and scaly. A pacifier can trap saliva and create an identical picture in younger children.
While dental products (mouthwash, toothpaste, dental floss or chewing gum) and medicaments (neomycin, bacitracin, budesonide, tetracaine) were among the third most common allergen sources for isolated allergic contact cheilitis, spillover to the perioral skin can also be seen. This is particularly seen in the case of toothpaste-driven allergic contact dermatitis. Both the foaming action of the toothpaste and the movement of the brush contribute to the spread of the toothpaste contactants. Clinically, this can be seen as contact dermatitis at the angles of the mouth. Another helpful clue is that the angles are affected in an asymmetric fashion with the side on which the toothbrush is held showing more involvement. This is typically the right side in right-handed individuals (Figure 3).
When allergic contact dermatitis of the oral cavity, lip and perioral region is suspected, empiric use of minimally allergenic or hypoallergenic products is recommended. Petroleum jelly may be used as a lip moisturizer. This is particularly helpful in the case of irritant dermatitis in lip lickers. Individuals should use only plain petroleum jelly and avoid formulations that may have other ingredients. Products such as Vaseline Advanced Formula Lip Therapy will have product labels stating “Active Ingredient: White petrolatum (100%)” portraying pure petrolatum jelly, but such products actually have inactive ingredients such as flavor. Tom’s of Maine Children’s Fluoride-Free Silly Strawberry Toothpaste is a nice, hypoallergenic toothpaste to keep in mind for empiric use in cases of suspected toothpaste allergy to cinnamon. For patients who react to acrylates in dentures, prolonged boiling of the dentures has been reported to polymerize residual acrylate monomers, thereby decreasing the allergenicity.
Ms. Huynh is with the Center for Dermatology Research and the department of dermatology at Wake Forest University School of Medicine in Winston-Salem, NC.
Mr. Chung is with the Center for Dermatology Research at Wake Forest University School of Medicine.
Dr. Sheehan is with the departments of dermatology at Indiana University School of Medicine and Richard L. Roudenbusch Veterans Hospital in Indianapolis, IN, and Dermatology Physicians, Inc. in Columbus, IN.
Dr. Zirwas is with the Department of Dermatology at Ohio State University in Gahanna, OH.
Dr. Feldman is with the Center for Dermatology Research and the departments of dermatology, pathology and public health sciences at Wake Forest School of Medicine.
Disclosure: The Center for Dermatology Research is supported by an unrestricted educational grant from Galderma Laboratories, L.P.
Dr. Feldman has received research, speaking and/or consulting support from Galderma, Abbott Labs, Warner Chilcott, Aventis Pharmaceuticals, 3M, Connetics, Roche, Amgen, Biogen, Stiefel/GlaxoSmithKline and Genentech.
Dr. Zirwas receives consulting support from Coria Labs, Taro Pharma and SmartPractice.
Dr. Sheehan, Ms. Huynh and Mr. Chung have no conflicts to disclose.
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