Indian Journal of Dental Research

: 2012  |  Volume : 23  |  Issue : 5  |  Page : 674--676

Chlorhexidine allergy due to topical application

Nandita N Keni, Meena A Aras, Vidya Chitre 
 Department of Prosthodontics, Goa Dental College, Goa, India

Correspondence Address:
Nandita N Keni
Department of Prosthodontics, Goa Dental College, Goa


Chlorhexidine is commonly used in dentistry in various forms. Allergic reactions to chlorhexidine of both immediate and delayed type have been reported. Although the incidence is low there may be severe manifestations in some patients. This report presents a case of allergy to chlorhexidine following topical application.

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Keni NN, Aras MA, Chitre V. Chlorhexidine allergy due to topical application.Indian J Dent Res 2012;23:674-676

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Keni NN, Aras MA, Chitre V. Chlorhexidine allergy due to topical application. Indian J Dent Res [serial online] 2012 [cited 2023 May 31 ];23:674-676
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Full Text

Chlorhexidine is one of the most commonly used antiseptics and antimicrobial agents in dentistry. It is found in many antiseptic skin creams, gels, and mouth rinses, as well as in disinfectants used to prepare the skin for surgical procedures. As it is a commonly used drug it is important to be aware that chlorhexidine has been associated with a variety of hypersensitivity reactions, ranging from delayed hypersensitivity reaction like allergic contact dermatitis, [1] urticaria, [2] and fixed drug reactions [3] to immediate hypersensitivity reactions such as anaphylaxis. [4],[5],[6] This case report presents a case of allergy to chlorhexidine following its use as a topical gel.

 Case Report

A 50-year-old female patient reported to the Department of Prosthodontics, Goa Dental College and Hospital, requesting fabrication of a new set of removable partial dentures. On examination, the patient had bilaterally missing molars in the mandibular arch and missing right molars in the maxillary arch. On the first scheduled appointment, upper and lower alginate impressions were made. The patient was asked to come the next day for border molding, and a final impression using zinc oxide eugenol impression paste (DPI company) was made using the functional impression technique. The patient presented the next day with a white non-scrapable lesion on the lower lip near the corner of the mouth on the left side. There was no erythema or swelling. She did not have any systemic symptoms and there was no history of fever. She did not give history of previous occurrence of such lesions. There was no past history of any food or drug allergy. On the basis of the clinical signs and symptoms we diagnosed the lesion as chemical burns induced by zinc oxide eugenol. Accordingly, we advised topical application of chlorhexidine gel on the affected area and asked the patient to report after 2 days.

When the patient came after 2 days she had erythema , swelling, and vesicles on the lower lip, with a few vesicles also present on the upper lip. The patient gave history of applying chlorhexidine gel in the affected area, which was followed a few hours later by a burning sensation and the appearance of vesicles and swelling [Figure 1] and [Figure 2].{Figure 1}{Figure 2}

Reapplication of the gel by the patient after 6 hours was once again followed by a similar episode of burning sensation. After this second episode the patient discontinued the use of the gel.

The patient was advised an antihistaminic (1 tablet twice a day) for 2 days and with this treatment there was regression in swelling and erythema. The vesicles cleared completely after 6 days.

We suspected allergy due to chlorhexidine gel. A patch test was done to confirm the diagnosis. Skin patch test using 1% chlorhexidine gluconate was carried out 15 days after the episode. An erythematous patch was seen at the site of application after 24 hours, confirming our diagnosis.

Since a greater number of antigens can pass through damaged mucosa than through intact mucosa, there is correspondingly greater chance of allergic reactions in patients having damaged mucosa.


Chlorhexidine is one of the most commonly used antimicrobials. Its antimicrobial and antiplaque potential was first described by Loe and Schiott in the 1970s. Contact sensitivity to chlorhexidine was first reported by Calnan.

Allergic reactions to chlorhexidine after topical application can vary from minor symptoms like tingling, itching, and uticaria [2] to major reactions like anaphylaxis. [4],[5],[6] Fixed drug reactions after the use of chlorhexidine in the form of mouthwash have also been documented. [3]

Chlorhexidine is known to elicit contact dermatitis after prolonged or repeated application, but contact dermatitis from chlorhexidine may also result after a short exposure such as preoperative skin cleansing or disinfection of a puncture site. [4] Chlorhexidine is also reported to have caused allergic reactions, including anaphylactic reactions, after use as a skin disinfectant prior to central venous catheter insertion and urethral catheterization.

The use of chlorhexidine in dentistry is well known but it should be remembered that chlorhexidine is also present in various nonmedicinal products. Previous exposure to these can hence sensitize the patient, causing serious reaction on re-exposure. It has been suggested that the reactions following topical application of chlorhexidine are mediated by IgE antibodies against chlorhexidine and it is the whole chlorhexidine molecule that is complementary to the IgE antibody-combining sites on the sensitized basophils. Hence IgE antibodies that react with the chlorhexidine molecule can be found in the patient's serum.

The various tests that can be used to confirm allergy to chlorhexidine include patch test, prick tests, sulfidoleukotriene stimulation test (cellular antigen stimulation test; CAST), and lymphocyte transformation tests. A chlorhexidine skin test is the most readily available, most rapid, and most accurate diagnostic procedure, but it has a risk for anaphylaxis. Routine use of skin tests should be avoided as the test procedure might itself, in some cases, sensitize the patient. Patch tests are generally done to test for delayed hypersensitivity and prick tests for immediate hypersensitivity. More sophisticated tests like lymphocyte transformation tests have not been found to be superior to the skin test in sensitivity and specificity. [4]

In this patient, chlorhexidine allergy was suspected as chlorhexidine was the only active ingredient in the gel. Also chlorhexidine is known to cause allergic reactions on topical application, even in low concentrations. Allergy to eugenol was not considered based on the clinical signs and symptoms and the history given by patient. After making lower impressions with eugenol, the patient presented with symptoms characteristic of eugenol burns. There was no erythema or swelling as is seen in allergic reactions. It was only after using chlorhexidine that the patient presented with symptoms of allergy (vesicles, erythema, and swelling). Also, repeat application of chlorhexidine produced the same reaction again.


Chlorhexidine, in various forms, is widely used in dentistry. Hence it is important that the dentist be aware of the adverse effects of chlorhexidine. The initial manifestations of allergy may be mild but reapplication can lead to a fatal reaction and hence even mild reactions should not be ignored. To conclude, hypersensitivity to chlorhexidine is rare but possible and therefore dentists should be alert to this possibility.


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