Minoxidil is one of the most popular and effective hair growth treatments. It has been used for decades to improve hair density in widespread conditions such as androgenetic alopecia [1]. But while it is safe and effective for humans when taken appropriately, research has highlighted the harmful effects of Minoxidil in cats and dogs.
Studies show that 46.6% of cats and 32.1% of dogs who were directly exposed to this medication developed clinical signs of toxicity [2]. While more than half of pets exposed to small quantities of Minoxidil are completely fine, some unfortunate cases were lethal. Here, find out all you need to know about the effect of Minoxidil on cats and dogs, such as:
Yes, Minoxidil can be dangerous for cats and dogs even if they’re exposed to small amounts of this substance. One 2021 study [2] analysed 211 cases of pet exposure to topical Minoxidil. While most of the animals recovered, the authors found that 87 of the animals (62 cats and 25 dogs) developed clinical symptoms of Minoxidil toxicity. Out of those who did so, 56% of dogs and 59.7% of cats developed moderate or major illness, while 12.9% of the affected cats did not survive.
Since they are smaller animals, cats are particularly sensitive to ingesting even tiny amounts of Minoxidil, such as from licking your hand after having applied it to your scalp. They can also be harmed if the solution gets on their skin [2].
As this medication is a vasodilator, it widens their blood vessels, causing their blood pressure to decrease (sometimes to life-threatening values). Furthermore, studies show that cats who became very ill and died from Minoxidil toxicity also showed pulmonary oedema and an accumulation of fluid in their lungs which impeded their breathing.
Dogs seem to be more resistant to Minoxidil than cats and less susceptible to severe illness or death. That may be partly because most dog breeds are larger and weigh more than cats (studies don’t always mention the breed of dog exposed to the medication). However, they too can experience low blood pressure after ingesting Minoxidil.
Scientists have used beagle dogs in clinical trials to test this drug and they have found that ingesting both topical and oral Minoxidil can cause the animals multiple types of heart lesions. However, simply having the topical solution applied to their skin was not found to be harmful to dogs [3].
On the contrary, in carefully controlled therapeutic doses, Minoxidil may have a similar hair growth effect as it does in humans, as discovered in a 2003 study that successfully grew fur on newborn, hairless pups [4].
Minoxidil – in all its forms – is generally considered safe and non-toxic for humans. However, this assessment was made under the assumption that people use this medication according to instructions, in the recommended doses. Unlike pets, humans are unlikely to swallow topical Minoxidil (or excessive doses of its oral form). In the isolated situations where that has happened, signs of toxicity were observed in people as well.
A 1999 case study describes the experience of a female patient who ingested 60 ml of Minoxidil 5% solution [5]. She experienced severely low blood pressure, abnormal heart rhythms and fluid buildup around her lungs. The authors warned that ingesting large quantities of Minoxidil can be very harmful and potentially lethal in humans as well as in animals. However, no severe side effects have ever been linked to the topical application of this drug in people [3].
While animals may react differently to Minoxidil exposure, there are some common warning signs that your pet may have come in contact with this drug. In both cats and dogs, the most frequently encountered symptoms include [3][6][7]:
This list isn’t exhaustive, so if your cat or dog displays any unusual or worrying behaviour after potential Minoxidil exposure, it’s important to see a vet as soon as possible.
Studies [2] show that in both cats and dogs, some symptoms can start within an hour of exposure, while others can take hours or even up to almost 3 days to develop (the longest recorded time to symptom onset was 67 hours).
Digestive system effects such as vomiting and excessive drooling usually occur first, followed by hypothermia after 3-4 hours. Lethargy may set in any time between 3 hours and 3 days after exposure.
If left untreated, your cat or dog can become ill quickly. So if you suspect they may have ingested or been exposed to Minoxidil, it’s important to seek veterinary treatment immediately.
Minoxidil exposure doesn’t necessarily mean directly or purposely applying the solution to your pet’s coat. Pets can also ingest Minoxidil by accident, or get it on their skin from drops fallen on the floor. However, research shows that there are some differences in the main ways cats and dogs are normally exposed to Minoxidil [2]:
Cats can climb and reach high surfaces with ease, so they can gain access to dressing tables and counters where they may be splashed with Minoxidil lotion. They are also known to groom themselves frequently by licking their fur (and ingesting anything that is on it).
88.7% of cats treated for Minoxidil exposure either licked the Minoxidil off their owner’s skin (hands or scalp) or licked their own fur after being accidentally splashed with it while the owner was applying it.
Dogs may not groom themselves as extensively as cats, but they are curious creatures and often eat what they’re not supposed to. 88% of the dogs who became ill after being exposed to Minoxidil chewed on an empty container found in the trash or ate tissue paper that the owner had used to clean off the excess hair loss medication[2].
Minoxidil is toxic for both cats and dogs, so it’s important to avoid exposing them to this treatment in any way.
The best thing you can do when you realise that your pet may have been exposed to Minoxidil is to take them to the vet immediately. While not all cats and dogs develop clinical symptoms from this drug, some cases can be life-threatening.
However, if you don’t have immediate access to veterinarian services, there are still some things you can do to improve your pet’s outcome:
Yes, most pets recover from Minoxidil poisoning. One study found that more than 87% of pets got better after being exposed to this drug [2].
However, this often depends on speedy medical treatment and ongoing monitoring. So you should take your pet to the vet as soon as you suspect Minoxidil poisoning.
Minimise the risk of exposing your pet to Minoxidil by taking the following precautions:
Cats in particular are notorious climbers and jumpers, so you need to store your Minoxidil securely. Keep it in a cupboard in an area your cat can’t access, such as your bathroom cabinet. Remember to keep the bathroom door shut.
When you dispose of any Minoxidil packaging, take it to your outside bin as soon as possible to make sure pets can’t accidentally find it in the house. Do the same with any tissue or swab you may have used to wipe off excess lotion.
It’s good practice to wash your hands after applying Minoxidil regardless of whether you have a pet. Otherwise, the solution can easily spread to other areas of your body. However, if you have a cat or dog, washing your hands is essential to avoid transferring any of the solution to your pet’s coat.
If your pet has a habit of licking you, it’s important to stop or limit this behaviour. Licking areas of your face or body where Minoxidil has been applied is one of the most common ways pets become exposed to this substance [2].
Apply Minoxidil at least an hour before you go to bed to give the solution time to absorb into your scalp before you sleep. This can stop medication from getting on your pillowcase and being transferred to your pets via your bed.
If possible, apply Minoxidil in a room you can make off-limits to your pets. If you can’t keep them out of that space at all times, at least make sure they are not in the same room with you while you apply it. This helps avoid splashing on their coats, inhaling vapours or spills on the floor that they lick before you have a chance to stop them.
If you feel your pets are unsafe around Minoxidil and you would like to find a treatment that is as effective but more animal-friendly, it is best to get the advice of a specialist. Book a consultation today with one of our experienced trichologists and they will work together with you to find a Minoxidil alternative that suits both your pet’s safety and hair growth needs.
Depending on the condition that is causing your hair to fall out, they will recommend the best hair loss treatment for men (or, respectively, the most effective hair loss treatment for women) which is also non-toxic to your furry friends. This may be another hair growth medication, such as Finasteride, or a noninvasive treatment such as red light therapy for hair growth. Or – if you are a good candidate – you could even get a permanent hair transplant which can solve your hair loss problems forever.
If you still have questions about the toxic effect Minoxidil can have on your pets, find out more from the answers to these common queries:
By all means, it is possible to use Minoxidil if you have a cat or dog — you just need to take the right precautions and be vigilant about protecting your pets from exposure. Many pet owners use this treatment with no mishaps because they are responsible for the way they store, apply and dispose of their medication.
If a cat swallows Minoxidil pills, there is a good chance the medication will cause harm. However, it’s unlikely that cats will chew and swallow these pills accidentally. Dogs are more prone to ingesting pills because of their love of chewing.
However, the oral Minoxidil will only harm them if they swallow enough of it – upwards of 0.5 mg/kg [8]. So if your dog weighs over 10 kg and he swallowed a single 5 mg pill, it is likely it will be OK. However, it is still a good idea to have them checked out by a vet as soon as possible.
That largely depends on your pet’s species and the quantity of Minoxidil it ingests. Research found this medication to be relatively non-toxic to rats [9]. Miniature pigs also only seemed to be harmed by this drug in experimental settings, when given oral doses of 10 mg/kg, but were fine after ingesting 1 or 3 mg/kg [8]. And at this time, no research has been conducted to show whether Minoxidil is safe for birds, reptiles or other types of pets.
While there are no specific studies made to determine the impact of Minoxidil spray vapours on cats and dogs, if your pets inhale too much, it might harm them (especially cats and small dogs). So be sure to remove your pets from the room before spraying Minoxidil on your scalp and keep a window open afterwards.
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