The clinical signs and symptoms of contact oral allergy are nonspecific and are frequently difficult to distinguish from physical irritation. The reaction occurs only at the site of contact and includes a burning sensation or soreness accompanied by erythema, and occasionally the formation of vesicles and ulcers. Burning sensations without the presence of lesions is not a result of contact allergy, and obtaining allergy tests for patients with burning mouth syndrome with normal-appearing mucosa is not indicated.
Lesions that appear lichenoid both clinically and histologically may also be a result of contact allergy when the lichenoid lesion is in direct contact with the potential allergen. These lesions occur most frequently as a result of mercury in amalgam, and appear on the buccal mucosa and lateral border of the tongue in direct contact with the restoration. These lesions disappear when the amalgam is removed. It should be emphasized that there is no evidence that generalized lesions of oral lichen planus not in direct contact with restorations heal when amalgam restorations are removed.
Another oral manifestation of contact allergy is plasma cell gingivitis, which is characterized by generalized erythema and edema of the attached gingiva, occasionally accompanied by cheilitis and glossitis(Figure 4-16). The histopathology is described as sheets of plasma cells that replace normal connective tissue. Some cases have been related to an allergen present in toothpaste, chewing gum, or candy, whereas other cases remain of unknown etiology even after extensive allergy testing. Plasma cell gingivitis must be distinguished from neoplastic plasma cell diseases such as plasmacytoma or multiple myeloma.
