Boric acid is used for the treatment of non-Candida albicans vulvovaginal candidiasis and recurrent bacterial vaginosis in the form of vaginal suppositories or capsules, and it is available in some countries in topical preparations such as solutions, ear and eye drops, and ointments, including antiseptics for burns. It is also used in the manufacturing of ceramics, glass, and pesticides and as a wood preservative and thus may be distributed in public spaces via the air, water, and soil and in sewage systems. Furthermore, boric acid and borate salts are commonly found inside homes, hospitals, and commercial buildings.

Accidental or intentional ingestion may be toxic or even lethal. Lethal doses of ingestion are 5-6 g in children and 15-20 g in adults. An overwhelming majority of acute cases are seen in children younger than 6 years (median age: 2 years) via accidental ingestion. Adult intoxication can be accidental or intentional.

Typical signs and symptoms of acute toxicity from ingestion begin with gastrointestinal upset (eg, blue-green vomit and diarrhea, which may be bloody). Some cases can progress to hemodynamic shock and lactic acidosis requiring fluid resuscitation and pressors. Subsequently, a widespread erythematous macular and papular eruption appears that starts on the trunk and head and progresses outward. This is followed by desquamation. There may also be conjunctival injection and pharyngeal erythema. Neurologic symptoms and signs then develop, including headache and confusion in adults, meningismus in children, and convulsions. Acute tubular necrosis, hyperthermia, and shock may ensue.

Chronic low-dose exposure to boric acid may occur in adults secondary to inhalation in the occupational setting, such as where boron is mined or processed, and may manifest as dry mucous membranes, sore throat, dry cough, and epistaxis.

Finally, topical exposure to boric acid may lead to severe irritant dermatitis with erythema, oozing, weeping, and crusting of the exposed area. This may be accompanied by pain, burning, or pruritus.