WASHINGTON — A popular zinc-based homeopathic remedy for the common cold that is sold over the counter is not only ineffective but can cause users to lose their sense of smell, a study published Monday warned.

Clinic trials found that zinc nasal gels and sprays were ineffective in preventing or reducing the duration of the common cold, as well as links to a loss of smell, the study in Archives of Otolaryngology said.

The authors of the study sounded the warning about zinc nasal cold remedies after evaluating 25 patients and analyzing reports of clinical, biological and experimental data.

Only one of the studies analyzed showed that zinc therapies reduce the severity of a cold -- but it was funded by the makers of the medicine used in the study.

"In addition to concerns regarding the efficacy of intranasal zinc therapy, increasing evidence indicates that this medication may be linked to severe, potentially permanent hyposmia (reduced sense of smell) and anosmia (loss of smell)," the study says.

In the light of their findings, the authors urged the US Food and Drug Administration (FDA) to more strictly regulate zinc cold therapies and other homeopathic remedies.

"Only homeopathic drugs offered for treatment of 'serious disease conditions' must be dispensed by a licensed practitioner," the study said.

Homeopathic products that treat less serious illness, such as the common cold, can be sold over the counter and are exempt from "the rigorous premarket approval process that allopathic medications must go through before entering the market," the authors of the study said