BERLIN - “He smells old.” Whenever the 41-year-old woman hugs her father, that’s the first thought that crosses her mind. She’s right and her dad is no exception. Body odor changes over the course of a life, and older people do smell differently than younger ones.

"This has always been suspected, but now a study has shown that it’s true," says Professor Jessica Freiherr, a smell researcher at the Aachen University Hospital, in Germany. In the Philadelphia study she’s referring to, younger subjects had no trouble accurately identifying the smell of older subjects.

But there was one big surprise: by comparison with the smell of younger and middle-aged people, the “old” smell was described as the nicest and least strong. The smell of young to middle-aged men was described as being the worst.

The reason for that is the male hormone testosterone , the metabolites of which exude a strong smell. Unsurprisingly, the smell of women was perceived as much more neutral.

That participants in the American study found the smell of older people agreeable is, according to Freiherr, down to the fact that they actually didn’t know what they were smelling: "If they had been told it was old peoples’ sweat , the evaluation would most certainly have been different."

To conduct the study, pads were sewn into shirts and people were asked to wear the shirts for three days. Subjects were then asked to smell the pads .

"Context is very important to smell. If somebody thinks of a sock while smelling cheese, they will describe the cheese as smelling like feet,” she says. She believes the idea that old people smell bad probably came from the various smells that assail the nostrils in many retirement homes.

Body odor is the result of the components of sweat being broken down by bacteria. Sweat is 99% water that evaporates . Other components include sugar, ammonia, urea and body salts like sodium.

Bacteria like it best where it’s warm and damp – places like armpits, feet packed tightly into shoes, even the folds of very pronounced wrinkles. There’s a lot for them to feed on in such places, so they multiply rapidly and at some point begin to smell bad.

Some older people smell less strong than they did when they were younger . As hormone levels decline, the protective subcutaneous fat layer of skin is lost, and gland secretions change. If they do have a strong body odor (and this applies not only to older people) this can be due to any number of things. Poor hygiene, alcohol consumption, cigarette smoking, certain foods and being overweight all have a negative impact on body odor.

A mustiness

"Another reason for body odor in older people are the illnesses that frequently come with age," says Dr. Heiko Grimme, a Stuttgart-based dermatologist. The breath of people with kidney ailments smells like urine, for example. And incontinence is another issue with older folks.

Additionally, older people may be taking medication that changes body odor. Other reasons cited by Grimme are that some older people use soaps and scents that smell “old” to others, or a musty smell of old furniture gets into their clothes.

In many people 55 and older, the sense of smell starts to diminish so they may not be as aware as a younger person of how they smell.

Grimme advises elderly people to become aware of all these things and to be sticklers for personal hygiene: "You can’t let yourself go." Freiherr says that it is helpful for people with strong body odor to stick to wearing cotton or clothing made of other natural fibers .

Clothes that have been worn should on no account be returned to the closet. They must be laundered, otherwise "the bacteria remain in them and go on living in the closet."

For those suffering from incontinence, Birgit Huber of the IKW, the Frankfurt -based industrial association for body care products and detergents, recommends absorbent products like pads or incontinence underwear. Over four million people in Germany suffer from incontinence, most of them over 65.

" Perfumed hair and skin products are a good idea along with a powerful deodorant for those suffering from strong body odor," she says. Deodorants stop the proliferation of bacteria, and hide the smell. They should be applied to clean skin. There are also antiperspirants that stop or reduce sweating so less bacteria are produced and the wearer’s body odor stays decent.

Any advice for those who live or work with older people whose body odor is unpleasant? "Always address the issue, otherwise these folks may find themselves getting isolated because others don’t want to be around them," says psychotherapist Christa Roth-Sackenheim.