Astringent agents

Agents used for tanning with astringent properties have been used for hyperhidrosis.[58,148] These agents denature keratin proteins in the stratum corneum layer lining the sweat pore, which leads to a superficial closure of the pore that lasts several days, until reparative desquamation of the cell layer occurs.[58] Acids and aldehydes such as formaldehyde, glutaraldehyde, tannic acid, and trichloroacetic acid have all been used to treat hyperhidrosis.[58] These agents are now essentially considered obsolete, although low concentrations of astringents may be found in some commercial preparations.[58]

Formaldehyde induces contact sensitivity, leading to allergic contact dermatitis in 15% to 20% of patients.[58] Methenamine, used systemically as a urinary tract antiseptic, releases formaldehyde in the presence of acid. Methenamine, contained in several commercial products, has been successfully used as a topical agent for hyperhidrosis by slowly releasing formaldehyde in the presence of acid eccrine sweat.[15,58] Patients using commercially prepared stick antiperspirant with 5% methenamine had a significant improvement in palmoplantar sweating (P<0.001) and no development of allergic contact sensitization.[15] In another study, 24 of 26 patients had decreased palmar and plantar sweating with use of the 5% methenamine stick; one patient with prior allergic contact dermatitis due to formaldehyde had no reaction to methenamine.[30]

Glutaraldehyde is another tanning agent that has been used to treat hyperhidrosis.[68] Patients who are sensitized to formaldehyde did not react to glutaraldehyde.[68] A 10% glutaraldehyde solution decreased sweating on the soles of all 25 patients treated, but had no clinical effect on axillary hyperhidrosis.[68] Yellow-brown discoloration occurs in the skin with use of glutaraldehyde, and thus it may only be clinically useful on the soles.[148] Tannic acid is less effective than glutaraldehyde and can also cause skin discoloration.[148]