Take note, kids; next time pumpkins or squash is on the menu, ask your parents how they'd feel if it made you lose your hair.

According to a recent case study two women experienced alopecia just weeks after downing a meal made from bitter varieties of these two vegetables.

The surprising effects have never been seen before, so are clearly extremely rare. Still, it's a far better excuse than "I couldn't fit in another bite".

Dermatologist Philippe Assouly from Saint Louis Hospital in France traced the cause of spontaneous hair loss in two women back to cucurbit poisoning, in one case from a pumpkin soup and another from a side dish of squash.

Keep in mind, these aren't just typical vegetables you'd pick up in most grocers.

Most garden variety members of the cucurbit family, which include pumpkins, cucumber, zucchini, and squash, have been selected over time to have the barest amounts of a bitter compound called cucurbitacin.

Ancestors of the vegetable evolved the chemical to dissuade herbivores from chowing down, but clearly there will always be some people who fail to get the message.

It's not uncommon for those who have acquired a taste for bitter flavours (or simply don't notice them) to include such gourds in soups and other consumables. Concentration of cucurbitacin can increase in homegrown varieties if the plant has not had enough water, or accidentally cross pollinated by your friendly neighbourhood pollinators.

Unfortunately, cucurbitacin does more than abuse your taste buds – it's known to be toxic in doses that are small enough to fit on a plate.

Online gardening blogs are full of words of wisdom describing the "stomach cramps, diarrhoea … and a pounding heart" that can come with eating too much of these drought-stressed or hybridised cucurbit.

Hey, it's not like the plant isn't doing its best to warn you.

While medical reports of cucurbitacin poisoning typically describe bad things coming out both ends, none have so far included trichorrhexis nodosa – a change to the structure of hair shafts that causes them to snap off.

That make this case study a new addition for the medical books.

Assouly notes that in both cases the patients experienced digestive problems shortly after eating bitter tasting cucurbits in the form of a soup or as a side dish.

In the case of the side dish, other dinner party guests turned down their helpings of the vegetable on account of its taste, which only added to the dermatologist's suspicions.

Similarly, other family members of the second subject apparently weren't a fan of the soup, so turned it down in favour of something less toxic.

The patients' nausea and diarrhoea reportedly eased up after a period of around 24 hours, but that wasn't the end of their woes.

Within several weeks, both women found they were losing hair on their scalp and from other parts of their bodies.

Even months later, some of the regrowth was still showing signs of breaking off at a weakening 2 to 6 centimetres (about an inch or two) from the base of the hair's shaft.

The case study doesn't say whether the two subjects eventually recovered, so we can only hope it's a temporary effect.

But Assouly is convinced that he knows what caused it.

"Acquired trichorrhexis nodosa supports the diagnosis, with the length of the hair that grew after poisoning matching the length of the new hair growth," the dermatologist writes in the Journal of the American Medical Association report.

There's no word on what the mechanism might be behind this form of alopecia, so it could be worth researchers digging deeper.

The take home message for the rest of us is to pay attention to those bitter notes in your home-grown pumpkins, just in case they're producing a little too much toxin after cross-pollinating with a wild cousin.

If your stomach doesn't thank you for it, your head just might.

This research was published in in JAMA Dermatology.