Here are some of the side effects from the active ingredient in these chews (chlorhexidine gluconate) in humans.
“Applies to chlorhexidine topical: compounding liquid, mucous membrane insert, mucous membrane liquid, topical dressing, topical liquid, topical pad, topical soap, topical solution, topical sponge
Gastrointestinal
In clinical trials, 56% of chlorhexidine oral rinse users had a measurable increase in staining of teeth, and 15% experienced heavy staining. Stains may generally be removed by conventional professional prophylactic techniques. Staining of rough areas may be permanent. Stains are general dark brown to blackish.
Staining will be more pronounced in the presence of heavier accumulations of unremoved plaque.
Staining due to chlorhexidine may be due to the interaction with dietary compounds such as coffee and tea.[Ref]
Gastrointestinal side effects have been reported the most frequently with chlorhexidine oral rinses. These have included staining of teeth and tongue, increased calculus formation, alteration of taste perception, bitter taste, burning, numbness, dryness, and soreness. Aphthous ulcer, grossly obvious gingivitis, trauma, ulceration, erythema, desquamation, coated tongue, keratinization, geographic tongue, mucocele, and short frenum have been reported rarely with chlorhexidine oral rinses. Gastrointestinal side effects associated with chlorhexidine oral rinses without oral hygiene measures have included increased gingival bleeding after gentle massage.
Parotid gland swelling has been reported rarely.
Gastrointestinal side effects associated with chlorhexidine cleanser have included a single case report of acute gastritis.
Gastrointestinal side effects associated with chlorhexidine cleanser enema have included a single case report of acute colitis.
Gastrointestinal side effects associated with the periodontal chip have included transient toothache (50.7% vs 41.4% placebo), including dental, gingival, or oral pain, tenderness, aching, throbbing, soreness, discomfort, and sensitivity.[Ref]
Hypersensitivity
Hypersensitivity reactions to chlorhexidine have included allergic contact dermatitis, pruritus, vesicle formation, urticaria, dyspnea, and anaphylactic shock.[Ref]
Hypersensitivity reactions have been reported after the use of products containing chlorhexidine as a preservative or devices coated with chlorhexidine, including allergic contact balanitis and anaphylactic shock.
Patch testing using chlorhexidine has revealed positive reactions in more than 2% of patients tested. In eczema patients, the rate may be as high as 5%.[Ref]
Ocular
Exposure of the eye to chlorhexidine cleanser, generally during preparation for facial surgery, has resulted in eye pain, edema of the epithelium, keratitis, inflammation of the conjunctiva, corneal epithelial cell loss, chronic corneal ulcers, and opacification. Corneal transplantation to correct permanent damage has been required in some patients.
Allergic conjunctivitis is rarely associated with the use of contact lens solutions which contain low concentrations of chlorhexidine as a preservative.[Ref]
Ocular side effects associated with chlorhexidine cleanser have included ocular toxicity.
Ocular side effects associated with chlorhexidine containing contact lens solutions have rarely included allergic conjunctivitis.[Ref]
Nervous system
Nervous system side effects have included cases of sensorineural deafness following direct instillation of chlorhexidine into the middle ear.
Nervous system side effects associated with insertion of the periodontal chip have included headache (27.1% vs 27.5% with placebo chip)
