Minoxidil has become so ubiquitous in the conversation around hair loss that we rarely stop to question what it actually is—or what risks come with keeping it in our homes.

Originally developed as a blood-pressure medication, minoxidil is a potent vasodilator that later became an FDA-approved treatment for certain forms of hair loss. Today, topical minoxidil is available over the counter and oral minoxidil is increasingly prescribed off-label for hair loss.

It can work. That isn’t the controversy.

What deserves far more attention is everything that comes with it—particularly for women who are pregnant or planning pregnancy, people who experience its adverse effects, and households with cats or dogs.

And the pet issue is not hypothetical.

Minoxidil can be deadly to pets

Minoxidil is toxic to both cats and dogs, with cats appearing particularly vulnerable.

A study published in the Journal of the American Animal Hospital Association examined 211 cases of topical minoxidil exposure reported to the ASPCA Animal Poison Control Center.

Among the animals that developed clinical signs, researchers found that illness could occur after exposures as seemingly insignificant as a few drops or licks.

Of the 62 symptomatic cats included in the detailed analysis, eight died—12.9%.

Pets didn’t necessarily drink a bottle of minoxidil.

Cats were exposed after licking an owner’s treated skin, contacting contaminated pillowcases or being splashed during application. Dogs were also exposed through accidental contact and exploratory behavior.

The reported complications can be severe: hypotension, abnormal heart rhythms, pulmonary edema, pleural effusion, respiratory distress and cardiovascular compromise.

Published veterinary case reports document cats developing severe pulmonary edema and pleural effusions after topical exposure, and fatal cases have been reported despite intensive supportive care.

More recent poison-control data suggest that exposures are increasing. An analysis of animal poison-control reports from 2013 through 2024 found a substantial rise in minoxidil-related cases over that period.

The ASPCA now explicitly warns that minoxidil represents a serious and potentially fatal risk to pets, especially cats.

That means something as ordinary as your cat sleeping on your pillow after you’ve applied your hair treatment can potentially become an exposure route.

For anyone who shares their bed, bathroom or home with an animal, that deserves to be part of the hair-growth conversation.

What minoxidil can do to humans

Minoxidil is an effective medication for many people, and serious systemic reactions to properly used topical minoxidil are uncommon.

But “available over the counter” does not mean side-effect free.

FDA-regulated topical minoxidil labeling instructs users to stop treatment and consult a doctor if they develop:

• chest pain
• rapid heartbeat
• faintness or dizziness
• sudden unexplained weight gain
• swelling of the hands or feet
• scalp irritation or redness
• unwanted facial hair growth

Dermatologists also recognize dryness, scaling, itching and scalp irritation as common problems with topical minoxidil.

Contact dermatitis can occur either from minoxidil itself or other ingredients in certain formulations.

Another potential side effect is hypertrichosis—unwanted hair growth away from the intended treatment area, including facial hair.

Minoxidil can also cause an initial shedding phase. The American Academy of Dermatology notes that women can experience increased hair loss during approximately the first two to eight weeks of treatment before regrowth begins.

And there is another reality that is sometimes glossed over:

The results generally require continued use.

Minoxidil does not permanently “cure” the biological processes responsible for androgenetic hair loss.

If it works, continued treatment is typically required to maintain the benefit. When treatment stops, the benefit gradually disappears and shedding increases. Dermatologic references describe the pretreatment appearance generally returning within several months after discontinuation.

For some people that is an acceptable tradeoff. But consumers deserve to understand it before starting.

What about pregnancy and breastfeeding?

This is particularly important for women.

FDA-regulated OTC minoxidil labeling states that minoxidil may be harmful if used while pregnant or breastfeeding.

The American Academy of Dermatology advises women who are pregnant or planning pregnancy to avoid minoxidil and also advises breastfeeding women to avoid it.

Human pregnancy data are limited, which is precisely why caution is recommended.

Breastfeeding guidance is somewhat more nuanced in the medical literature: LactMed notes that topical minoxidil may be acceptable once breastfeeding is established but stresses that infants must not contact treated skin. Other dermatology guidance recommends avoidance because of the limited safety data.

For Agent Nateur, we believe women deserve to know that uncertainty rather than having it buried in fine print.

We wanted a different approach to scalp health

When we created holi (growth) 84, we wanted to formulate around the biology of the hair follicle without formulating with minoxidil.

At the center of the formula is Redensyl®, a patented cosmetic hair-care active designed to target pathways associated with the hair-growth cycle.

Redensyl isn’t simply a plant extract.

Its active system combines molecules derived from European larch and green tea with glycine and zinc.

Its key components include:

Dihydroquercetin-glucoside (DHQG)
Derived from larch, this stabilized polyphenol has been studied for its activity involving hair-follicle stem cells and dermal papilla fibroblasts.

Epigallocatechin-glucoside (EGCG2)
A stabilized molecule derived from green tea and investigated for antioxidant and cellular signaling activity.

Glycine
An amino acid involved in keratin-associated proteins.

Zinc
An essential mineral involved in numerous enzymatic processes and normal hair biology.

Rather than acting primarily as a vasodilator, Redensyl was developed to interact with biological pathways associated with the follicle and the transition of hair into its active growth—or anagen—phase.

The 84-day Redensyl clinical study

This is where the name holi (growth) 84 comes from.

In a double-blind, placebo-controlled supplier clinical study, volunteers with grade III-IV androgenetic alopecia applied a formula containing 3% Redensyl daily for 84 days.

After three months, the Redensyl group demonstrated:

+9% increase in anagen-phase hair

Anagen is the active growth phase of the hair cycle.

−17% decrease in telogen-phase hair

Telogen is the resting/shedding phase.

+29% improvement in the anagen-to-telogen ratio

In other words, the balance shifted toward growth-phase hair.

Approximately +8% average improvement in hair density

This corresponded to approximately:

+17 hairs per cm²

and an extrapolated average of approximately:

+10,200 hairs across a 600 cm² scalp surface.

Individual responders in the supplier data reached substantially larger calculated increases, with results reported as high as approximately 28,200 hairs.

Overall, 85% of participants were classified as clinical responders.

Among those responders, the changes were even greater:

+11% anagen hair

−20% telogen hair

+34% improvement in the anagen-to-telogen ratio.

Participants’ self-assessments also reported perceptions of reduced hair loss and improvements in density, strength and thickness.