Personal hygeine

I have a relative who seems to be allergic to soap, shampoo, and toothpaste. In a word, the woman stinks! Her kids are stinky too and their teeth have turned yellow-green from lack of toothbrushing. This woman has a college degree but has zippo common sense.
Question–how do you tell someone to bathe, brush their teeth, brush their hair, and generally keep themselves presentable to the public?
If it was just her–I’d just avoid the heck out of her–but her kids are suffering from this. As they enter adolesence, they have become increasingly unattractive due to lack of hygeine.
Thoughts, advice, wisdom?

Try gently reminding her that this could be considered by a school-teacher to be child neglect.

If she’s allergic to soaps - there are many possible options including simply bathing in water alone using oatmeal as a scrub to exfoliate and remove surface oils without drying the skin, using just baking soda to brush teeth, etc… as well as several gentle, hypoallegenic soaps and non-soap alternatives that available. Try the local health food or natural products store. If you have the means, you could offer the children a “spa day” (get creative here) and introduce them to a little cleanliness - A preteen female would likely be particularly responsive. If the children are on the ball, it probably hasn’t gotten past them that their personal habits are different than those of their peers. Maybe even just a little support from a trusted relative other than a parent to reinforce accepted societal hygeine standards is all they need.

The more you know, the less you understand - Tao Te Ching