Contact allergy results from a delayed hypersensitivity reaction that occurs when antigens of low molecular weight penetrate the skin or mucosa of susceptible individuals. These antigens combine with epithelial-derived proteins to form haptens that bind to Langerhans’ cells in the epithelium. The Langerhans’
cells migrate to the regional lymph nodes and present the antigen to T lymphocytes, which become sensitized and undergo clonal expansion. After re-exposure to the antigen, sensitized individuals develop an inflammatory reaction confined to the site of contact. Since the reaction resulting from contact allergy appears as nonspecific inflammation, contact dermatitis or stomatitis may be difficult to distinguish from chronic physical irritation. The incidence of contact stomatitis is unknown, but it is believed to be significantly less common than contact dermatitis for the following reasons:1. Saliva quickly dilutes potential antigens and physically washes them away and digests them before they can penetrate the oral mucosa.
2. Since the oral mucosa is more vascular than the skin, potential antigens that do penetrate the mucosa are rapidly removed before an allergic reaction can be established.
3. The oral mucosa has less keratin than does the skin, decreasing the possibility that haptens will be formed.
Contact stomatitis may result from contact with dental materials, oral hygiene products, or foods. Common causes of contact oral reactions are cinnamon or peppermint, which are frequently used flavoring agents in food, candy, and chewing gum, as well as oral hygiene products such as toothpaste, mouthwash and dental floss(Figure 4-15)
Dental materials that have been reported to cause cases of contact allergic stomatitis include mercury in amalgam, gold in crowns, free monomer in acrylic, and nickel in orthodontic wire.
62–64
Pyrophosphates and zinc citrate, which are components of tartar control toothpaste, cause superficial peeling of the mucosa in some users, but this reaction is believed to be caused by physical irritation rather than an allergic reaction.
62–64
Pyrophosphates and zinc citrate, which are components of tartar control toothpaste, cause superficial peeling of the mucosa in some users, but this reaction is believed to be caused by physical irritation rather than an allergic reaction.