Inside Topical Minoxidil's Toxic Threat to Household Pets

Medscape

12-05-2025

SAN DIEGO — New hair, new problems: A pair of reports are shedding light on the growing danger posed to household pets by topical minoxidil (Rogaine), the popular over-the-counter treatment for androgenetic alopecia.
One study, presented here at the annual meeting of the Society for Investigative Dermatology (SID), reported a 965% increase in minoxidil poisoning reports to the American Society for the Prevention of Cruelty to Animals (ASPCA) Animal Poison Control Center from 2013 to 2024, perhaps reflecting a 13-fold increase in Google searches for the drug.
And a scoping review of studies describing cases of minoxidil toxicosis in cats and dogs, published on April 4 in the Journal of the American Academy of Dermatology ( JAAD ), found that dogs were often exposed to minoxidil while rummaging through trash or chewing packaging, whereas cats were more likely to be exposed by lying on contaminated bedding or licking human skin.
Shari Lipner, MD, PhD
'Minoxidil's increasing popularity poses a preventable but growing threat to pets,' said Shari Lipner, MD, PhD, dermatologist at Weill Cornell Medicine, New York City, and a co-author of the study presented at SID, in an interview. 'Dermatologists must educate patients about risks, advocate for clearer product warnings, and emphasize immediate veterinary care if exposure occurs. Even small doses can be lethal, particularly for cats.'
Minoxidil, a vasodilator, was initially developed as an antihypertensive, and the topical formulation became a treatment for androgenetic alopecia in the 1980s.
The first reported poisoning of a pet — a dog — came in 2018, Lipner said, and more than 200 cases were documented by 2021.
However, 'we suspected that most dermatologists and their patients were unaware of the risk,' Lipner said. 'Our study is the first to examine whether the increasing popularity of topical minoxidil has led to more pet poisonings.'
Lipner and colleagues examined reports of minoxidil poisoning from the ASPCA Animal Poison Control Center and found that the number grew from 20 in 2013 to 213 in 2024. The study authors also examined Google Trends data and found that searches for minoxidil consistently rose from 2013 to 2024, reaching their highest level in 2024.
Why are pets so vulnerable to minoxidil? Cats don't have crucial liver enzymes needed for their bodies to process toxins in a process known as glucuronidation, 'making them unable to safely metabolize chemicals like minoxidil,' said Eric McMullen, MD, a dermatology resident at the University of Toronto, Toronto, Ontario, Canada, and a co-author of the journal study. 'In cats and dogs, the potent cardiovascular effects of topical minoxidil pose serious risks to a pet's heart and lungs,' he told Medscape Medical News .
Sharon Gwaltney-Brant, DVM, PhD, a veterinary toxicologist and adjunct professor at the University of Illinois Urbana-Champaign's College of Veterinary Medicine, told Medscape Medical News that their smaller body sizes also make cats more susceptible, 'which means it takes less total amount of drug to have an effect compared with larger species such as dogs and humans.'
Gwaltney-Brant, co-author of a landmark 2021 study on minoxidil toxicity in dogs and cats, added that 'the grooming behavior of cats may increase exposure to minoxidil that gets on their coats via spills, pillowcase residue, etc. Several cases of cats licking their owner's scalps following minoxidil application have been reported.'
For her part, Lipner noted that pets may also be exposed by licking contaminated sinks or chewing discarded bottles. 'While rare, we discovered cases where pet owners intentionally applied minoxidil to animals, likely trying to help with pet hair growth.'
Specifically, the scoping review published in JAAD found that dogs were more likely to have been exposed through 'exploratory' behavior like rummaging through trash or eating packaging (88% of the cases), while cats were mostly exposed indirectly through methods like licking human skin or lying on contaminated bedding (96% of cases).
For that review, McMullen and co-authors examined four single-incident reports and two case series of minoxidil poisoning in pets (68 cats; 26 dogs; average age, 3.6 years; mean weight, 5.5 kg). In more than half of the reported cases, the pets had no symptoms, but 97.8% of the pets had to be hospitalized.
The pets were exposed orally (70.2%), dermally (9.6%), or both (20.2%). The most common symptoms were hypotension (43.6%), lethargy (33.3%), tachycardia (27.7%), and tachypnea (21.3%). All dogs survived, but 10 (14.7%) cats died.
The study presented at SID examined 267 cases in dogs and 434 in cats from 2013 to 2024: 77% of pets were exposed orally, 4.9% dermally, and 15.8% both orally and dermally. Six pets were exposed by inhalation, one aurally, and one ocularly. The exposure method was unknown in eight pets.
In 54% of cases, the pets had no symptoms, and three cats died.
With regard to prevention, Lipner said, 'dermatologists should warn pet owners to store minoxidil securely (eg, locked cabinets), wash hands immediately after applying it, keep pets away from treated areas (eg, do not let cats lick your skin or sleep on your pillow after use), and dispose of bottles in sealed trash bins that pets will not be able to open,' Lipner said.
For his part, McMullen emphasized the importance of discarding any used tissues, cotton pads, or gloves in a sealed bin, and he said pets should be limited from sleeping on beds. 'Switching to oral minoxidil is also a reasonable option when the above measures are not possible,' he said.
Moving forward, 'ideally, these risks to pets would be explicitly listed in product labelling and monographs, which is currently not the case,' said journal study co-author Jeffrey Donovan, MD, PhD, assistant professor in the Dermatology and Skin Science at the University of British Columbia, Vancouver, British Columbia, Canada, in an interview. 'As awareness grows, we hope that fewer and fewer pets will be harmed by toxic drug interactions.'