Why do kids smell? Understanding BO, puberty and personal hygiene in children

If you’ve recently noticed your child coming home from school with smelly underarms, sweaty jumpers, or the first signs of BO in kids, you’re certainly not alone. For many parents, it can come as a surprise, one day your child still seems so little, and the next, you’re noticing the early signs that their body is beginning to change. In fact, body odour in kids is often one of the very first signals that puberty is starting.

Scientists at Germany’s Erlangen-Nürnberg’s Aroma and Smell Research Facility have discovered that the chemistry of body odour changes dramatically during puberty. Researchers noted that teenage sweat contains specific compounds that can smell like cheese, goats, or even urine. The 2024 study analysed the chemical makeup of underarm sweat and confirmed that puberty-linked hormones activate glands and skin oils in ways that make BO much more noticeable as children grow.

It was smelly moments like these that inspired blossom & beau. Founded by Amanda, a dedicated NHS paramedic and mum of five, the brand was born from a deeply personal understanding of the challenges families face as children begin to grow up. Amanda saw first-hand how many parents were searching for a safe, child-friendly deodorant at an affordable price that could gently tackle BO in kids without exposing delicate young skin to harsh adult formulas.

As both a healthcare professional and a busy mum, she understood that this wasn’t just about staying fresh, it was about confidence. Helping young girls feel comfortable in their changing bodies, while giving parents peace of mind that they were choosing something designed specifically for younger, more sensitive skin, became her mission.

That lightbulb moment led Amanda to create blossom & beau: a gentle, natural deodorant brand that supports children through the early stages of puberty, helping them feel fresh, confident, and proud of their growing personal hygiene routine.

The good news? Smelly underarms and body odour are completely normal and understanding why kids smell can help parents navigate this time of change. 

Smelly underarms in kids: Is body odour one of the first signs of puberty?

Yes, body odour is often one of the first signs of puberty. Children sweat from a young age, particularly when they are active, playing sports, or rushing around at school, so sweating itself is nothing new. What changes as they begin to grow, however, is how the body produces sweat.

During the early stages of puberty, a second type of sweat gland, known as the apocrine sweat gland, begins to become active. These glands are mainly found in the underarm and groin area and are closely linked to hormonal development. The important thing to know is that sweat itself doesn’t actually smell.

What causes the odour is the natural bacteria that live on the skin. When sweat mixes with this bacteria, it begins to break down, creating the smell that parents often first notice on school uniforms, PE kits, or underarms. This is why smelly underarms in kids can seem to appear almost overnight.

Far from being a sign of poor hygiene, it is very often simply one of the earliest signs that puberty is beginning.

When do kids start to smell?

Most children start to develop body odour between the ages of 7 and 12, with some girls experiencing BO even earlier as one of the very first signs of puberty. For many parents, this can come as a surprise, as puberty is often expected to begin with visible changes such as growth spurts or mood shifts. In reality, smelly underarms and body odour are often among the earliest and most noticeable clues that hormonal changes are already underway.

For girls in particular, body odour can develop before other signs become more obvious, which is why it is often the first thing parents notice.

You may also begin to see other early signs of puberty, including:

• increased sweating

• slightly oilier skin or hair

• breast budding

• emotional changes

• periods of rapid growth

  
  

Because these changes often happen gradually, body odour can be the first thing that feels suddenly different. For many families, it’s one of those bittersweet reminders that childhood is quietly giving way to the pre-teen years.

It’s important to remember that every child develops at their own pace, so there is no exact “right” age for these changes to begin. Some children may start to smell from around 7 to 9 years old, while for others it may happen a little later, closer to the tween years.

What matters most is recognising that body odour is usually a perfectly normal part of growing up, rather than a sign that anything is wrong. More often than not, it is simply the body’s way of signalling that puberty is beginning and that it may be time to gently introduce new personal hygiene habits, such as daily showers and an age-appropriate deodorant, like blossom & beau’s natural deodorant for girls, thoughtfully created with young underarms in mind.

For more information, you can check out our blog on what age should girls start wearing deodorant. 

Why does my child still smell after bathing?

Even after bathing, children may still develop body odour later in the day because sweating continues once they are back at school, playing outside, or taking part in sports.

School jumpers, blazers, and synthetic PE kits can also trap odour more easily, holding onto smells long after the body itself is clean. As puberty begins and sweat glands become more active, BO can return more quickly than it once did, which is why bathing alone may no longer feel like quite enough.

This is often the point at which introducing a gentle natural deodorant, like blossom & beau, becomes a helpful next step.

Why is personal hygiene so important at this stage?

As children begin to experience the earliest signs of puberty, building healthy personal hygiene habits becomes an important part of everyday self-care. These routines help young girls understand what is happening to their bodies and feel more in control of the changes they are experiencing.

A simple morning ritual of showering, getting dressed, and applying deodorant can become a quiet confidence boost before the school day begins. At blossom & beau, we believe these moments of self-care should feel empowering rather than overwhelming, helping girls step into this new chapter with confidence with simple, easy-to-use solutions that are gentle and kind to delicate underarms.

blossom & beau: A gentle solution for body odour in tween and teen girls

When BO in kids becomes more noticeable, many parents naturally begin looking for a solution that feels safe, effective, and specifically designed for younger skin.

Unlike many adult deodorants, which can be overly strong, heavily fragranced, or drying, our natural deodorant for girls has been thoughtfully formulated for delicate young skin.

Made with naturally derived ingredients and carefully tested for sensitive skin, blossom & beau’s inaugural Dazzling Diva natural deodorant offers a gentle way to help manage odour while allowing skin to breathe comfortably.

Most importantly, it supports something far greater than freshness alone: confidence. For a young girl beginning to notice the changes that come with growing up, having a product that feels made just for her can make all the difference. If you are wondering what the best deodorant to start with is, check out our blog on the benefits of choosing a natural deodorant. 

If you’ve been wondering why your child suddenly smells different, the answer is usually a very normal one. Body odour is often one of the first signs that puberty is starting, and with the right support, this moment can become a positive introduction to self-care and confidence.

This ethos sits at the heart of the blossom & beau story. Created by Amanda from her own experience as a mum and healthcare professional, blossom & beau exists to help young girls feel fresh, supported, and proud of taking care of themselves as they grow.

Because growing up should feel beautiful.

You may also find the following articles useful: 

• The benefits of choosing an aluminium-free deodorant

• 5 reasons why young girls need deodorant 

• Aerosol vs roll-on deodorant for kids 

Why do kids start to smell: Frequently asked questions 

Is it normal for my child to have body odour?

Yes. Many children begin to develop BO between 7 and 12 years old as an early sign of puberty. This is a completely normal part of growing up.

Can children use deodorant safely?

Absolutely. Gentle, natural deodorants like blossom & beau are specially formulated for young underarms, helping manage odour without harsh chemicals that can irritate delicate skin.

Why do kids smell suddenly after bathing?

As puberty begins, sweat glands become more active. Even after bathing, sweat mixes with natural skin bacteria, which can create BO.

At what age should I introduce deodorant?

Many children start using deodorant around the time they first notice smelly underarms, often between 7 and 12 years old, depending on their individual development. Remember, there’s no right age and every child is unique. 

How can I help my child build good personal hygiene habits?

Encourage simple routines like daily showers, clean school uniforms, and gentle deodorant. Making personal hygiene easy and empowering helps boost confidence as little ones grow.