Keto Breath, Rash and Hair Shedding: Cosmetic Side Effects

The big keto side effect, the keto flu, gets all the attention, but a few smaller, more cosmetic ones catch people off guard and occasionally panic them. None is dangerous, all are well understood, and most pass on their own. Here are the three that come up most: keto breath, the keto rash, and hair shedding.

Keto breath

Many people notice their breath changes in the first weeks of keto, taking on a distinctive fruity, metallic or nail-varnish-like smell. The culprit is acetone, one of the ketones your body produces, some of which you breathe out. In a sense it is a sign the diet is working, since it means you are in ketosis, but it is not the most charming confirmation. The reassuring news is that it is temporary for most people, easing as the body adapts and gets better at using ketones rather than venting them. While it lasts, drinking plenty of water helps, as does ordinary oral hygiene and sugar-free gum or mints. It is a nuisance, not a problem, and it generally fades within a few weeks.

The keto rash

Less common, and more alarming when it appears, is the so-called keto rash, known medically as prurigo pigmentosa. It shows up as an itchy, red, net-like rash, typically across the trunk, neck and back, and it has been linked to being in ketosis, though it is genuinely uncommon. Nobody is entirely sure why it happens. The practical points are these: it is not dangerous, it often settles on its own, and in some people reintroducing a modest amount of carbohydrate to come out of deep ketosis for a while clears it, after which they can sometimes ease back in. Keeping the skin clean and avoiding irritation helps. If it is persistent, severe or you are unsure what it is, see a doctor, both to confirm what it is and because a doctor can treat it; do not just suffer a rash on the assumption it must be keto.

Hair shedding

The one that worries people most is hair. Some find that a couple of months into keto they are shedding noticeably more hair than usual. This is real, but it is rarely about keto specifically and almost never permanent. It is a phenomenon called telogen effluvium, a temporary increase in shedding that follows many kinds of bodily stress, including rapid weight loss and abrupt dietary change, regardless of the diet. The hair that sheds is being pushed into its resting phase early by the upheaval, and it grows back. The shedding typically shows up two to four months after the change and resolves over the following months.

The way to minimise it is to avoid the things that trigger it: do not crash-diet on very low calories, make sure you are eating enough protein, and make sure your diet is nutritionally complete rather than a narrow meat-and-cheese affair, since deficiencies can contribute. In other words, the plant-rich, adequately-fed version of keto is also the version least likely to cost you hair. If shedding is dramatic, prolonged or patchy rather than a general thinning, see a doctor, since that can point to something other than ordinary telogen effluvium, such as a thyroid issue or a nutrient deficiency worth checking.

The bottom line

Keto’s cosmetic side effects are mostly minor and temporary. Keto breath is acetone you are exhaling, a sign of ketosis that fades with adaptation and is managed with water and oral hygiene. The keto rash is uncommon, not dangerous, often settles on its own or with a little reintroduced carbohydrate, and should be shown to a doctor if it persists. Hair shedding is usually telogen effluvium from rapid change rather than keto itself, is temporary, and is best avoided by not crash-dieting and eating enough protein and nutrients. None is a reason to fear the diet, but persistent or severe versions of any of them deserve a doctor’s look.

This is general information about the ketogenic diet, not medical advice. Persistent rashes or hair loss can have other causes and should be assessed by a doctor. If you are pregnant, on medication, or managing a condition, seek professional advice before changing your diet.