A doctor warned Friday that bitter-tasting pumpkins and squashes can contain potent toxins, after two women were poisoned by their dinners and lost most of their hair.

French dermatologist Philippe Assouly described the two unusual cases in a scientific journal, highlighting a previously unknown "toxic association of alopecia (hair loss) with a common plant".

The plant family in question are cucurbits and include squashes, gourds, and pumpkins.

In the first case, a woman in France suffered nausea, vomiting and diarrhoea, which started soon after she ate a bitter-tasting pumpkin soup.

The symptoms lasted for about a day. Then a week later, she started losing hair from her scalp and pubis.

"The meal had been shared with her family, who had eaten less of the soup than she had, and they experienced symptoms of food poisoning but no hair loss," Assouly wrote in the Journal of the American Medical Association Dermatology.

A second woman experienced food poisoning with severe vomiting after a meal that included squash. Other diners had skipped the squash because it tasted bitter.

"About three weeks later, the patient experienced substantial hair loss on her head as well as severe alopecia on the armpits and pubic region," the doctor said.

Cucurbits can contain cucurbitacin, a toxic compound that gives off a bitter taste.

The bitterness is bred out of domesticated cucurbits. But sometimes insects moving from one field to another cross-pollinate a cultivated plant with a wild or ornamental one.

"Bitterness in a squash should serve as a warning," Assouly told AFP. "One should not force a child to finish it."

Three years ago, a German died of cucurbitacin poisoning after eating a courgette stew, the doctor said.

These are the first known cases of hair loss due to cucurbit poisoning.