Head hair comes in many colours, shapes and sizes, and hairstyles are often an expression of personal style or cultural identity.

Many different genes determine our hair texture, thickness and colour. But some people’s hair changes around the time of puberty, pregnancy or after chemotherapy.

So, what can cause hair to become curlier, thicker, thinner or grey?

Curly or straight? How hair follicle shape plays a role

Hair is made of keratin, a strong and insoluble protein. Each hair strand grows from its own hair follicle that extends deep into the skin.

Curly hair forms due to asymmetry of both the hair follicle and the keratin in the hair.

Follicles that produce curly hair are asymmetrical and curved and lie at an angle to the surface of the skin. This kinks the hair as it first grows.

The asymmetry of the hair follicle also causes the keratin to bunch up on one side of the hair strand. This pulls parts of the hair strand closer together into a curl, which maintains the curl as the hair continues to grow.

Follicles that are symmetrical, round and perpendicular to the skin surface produce straight hair.

Life changes, hair changes

Our hair undergoes repeated cycles throughout life, with different stages of growth and loss.

Each hair follicle contains stem cells, which multiply and grow into a hair strand.

Head hairs spend most of their time in the growth phase, which can last for several years. This is why head hair can grow so long.

Let’s look at the life of a single hair strand. After the growth phase is a transitional phase of about two weeks, where the hair strand stops growing. This is followed by a resting phase where the hair remains in the follicle for a few months before it naturally falls out.

The hair follicle remains in the skin and the stems cells grow a new hair to repeat the cycle.

Each hair on the scalp is replaced every three to five years.

Hormone changes during and after pregnancy alter the usual hair cycle

Many women notice their hair is thicker during pregnancy.

During pregnancy, high levels of oestrogen, progesterone and prolactin prolong the resting phase of the hair cycle. This means the hair stays in the hair follicle for longer, with less hair loss.

A drop in hormones a few months after delivery causes increased hair loss. This is due to all the hairs that remained in the resting phase during pregnancy falling out in a fairly synchronised way.

Hair can change around puberty, pregnancy or after chemotherapy

This is related to the genetics of hair shape, which is an example of incomplete dominance.

Incomplete dominance is when there is a middle version of a trait. For hair, we have curly hair and straight hair genes. But when someone has one curly hair gene and one straight hair gene, they can have wavy hair.

Hormonal changes that occur around puberty and pregnancy can affect the function of genes. This can cause the curly hair gene of someone with wavy hair to become more active. This can change their hair from wavy to curly.

Researchers have identified that activating specific genes can change hair in pigs from straight to curly.

Chemotherapy has very visible effects on hair. Chemotherapy kills rapidly dividing cells, including hair follicles, which causes hair loss. Chemotherapy can also have genetic effects that influence hair follicle shape. This can cause hair to regrow with a different shape for the first few cycles of hair regrowth.

Hormonal changes as we age also affect our hair

Throughout life, thyroid hormones are essential for production of keratin. Low levels of thyroid hormones can cause dry and brittle hair.

Oestrogen and androgens also regulate hair growth and loss, particularly as we age.

Balding in males is due to higher levels of androgens. In particular, high dihydrotestosterone (sometimes shortened to DHT), which is produced in the body from testosterone, has a role in male pattern baldness.

Some women experience female pattern hair loss. This is caused by a combination of genetic factors plus lower levels of oestrogen and higher androgens after menopause. The hair follicles become smaller and smaller until they no longer produce hairs.

Reduced function of the cells that produce melanin (the pigment that gives our hair colour) is what causes greying.

Theresa Larkin, Associate professor of Medical Sciences, University of Wollongong

This article is republished from The Conversation under a Creative Commons license. Read the original article.

With around one in 50 adults diagnosed with cancer each year, many people are faced with the difficult task of sharing the news of their diagnosis with their loved ones. Parents with cancer may be most worried about telling their children.

It’s best to give children factual and age-appropriate information, so children don’t create their own explanations or blame themselves. Over time, supportive family relationships and open communication help children adjust to their parent’s diagnosis and treatment.

It’s natural to feel you don’t have the skills or knowledge to talk with your children about cancer. But preparing for the conversation can improve your confidence.

Preparing for the conversation

Choose a suitable time and location in a place where your children feel comfortable. Turn off distractions such as screens and phones.

For teenagers, who can find face-to-face conversations confronting, think about talking while you are going for a walk.

Consider if you will tell all children at once or separately. Will you be the only adult present, or will having another adult close to your child be helpful? Another adult might give your children a person they can talk to later, especially to answer questions they might be worried about asking you.

Finally, plan what to do after the conversation, like doing an activity with them that they enjoy. Older children and teenagers might want some time alone to digest the news, but you can suggest things you know they like to do to relax.

Also consider what you might need to support yourself.

Preparing the words

Parents might be worried about the best words or language to use to make sure the explanations are at a level their child understands. Make a plan for what you will say and take notes to stay on track.

The toughest part is likely to be saying to your children that you have cancer. It can help to practise saying those words out aloud.

Ask family and friends for their feedback on what you want to say. Make use of guides by the Cancer Council, which provide age-appropriate wording for explaining medical terms like “cancer”, “chemotherapy” and “tumour”.

Having the conversation

Being open, honest and factual is important. Consider the balance between being too vague, and providing too much information. The amount and type of information you give will be based on their age and previous experiences with illness.

Remember, if things don’t go as planned, you can always try again later.

Start by telling your children the news in a few short sentences, describing what you know about the diagnosis in language suitable for their age. Generally, this information will include the name of the cancer, the area of the body affected and what will be involved in treatment.

Let them know what to expect in the coming weeks and months. Balance hope with reality. For example:

The doctors will do everything they can to help me get well. But, it is going to be a long road and the treatments will make me quite sick.

Check what your child knows about cancer. Young children may not know much about cancer, while primary school-aged children are starting to understand that it is a serious illness. Young children may worry about becoming unwell themselves, or other loved ones becoming sick.

Older children and teenagers may have experiences with cancer through other family members, friends at school or social media.

This process allows you to correct any misconceptions and provides opportunities for them to ask questions. Regardless of their level of knowledge, it is important to reassure them that the cancer is not their fault.

Ask them if there is anything they want to know or say. Talk to them about what will stay the same as well as what may change. For example:

You can still do gymnastics, but sometimes Kate’s mum will have to pick you up if I am having treatment.

If you can’t answer their questions, be OK with saying “I’m not sure”, or “I will try to find out”.

Finally, tell children you love them and offer them comfort.

How might they respond?

Be prepared for a range of different responses. Some might be distressed and cry, others might be angry, and some might not seem upset at all. This might be due to shock, or a sign they need time to process the news. It also might mean they are trying to be brave because they don’t want to upset you.

Children’s reactions will change over time as they come to terms with the news and process the information. They might seem like they are happy and coping well, then be teary and clingy, or angry and irritable.

Older children and teenagers may ask if they can tell their friends and family about what is happening. It may be useful to come together as a family to discuss how to inform friends and family.

What’s next?

Consider the conversation the first of many ongoing discussions. Let children know they can talk to you and ask questions.

Resources might also help; for example, The Cancer Council’s app for children and teenagers and Redkite’s library of free books for families affected by cancer.

If you or other adults involved in the children’s lives are concerned about how they are coping, speak to your GP or treating specialist about options for psychological support.

Cassy Dittman, Senior Lecturer/Head of Course (Undergraduate Psychology), Research Fellow, Manna Institute, CQUniversity Australia; Govind Krishnamoorthy, Senior Lecturer, School of Psychology and Wellbeing, Post Doctoral Fellow, Manna Institute, University of Southern Queensland, and Marg Rogers, Senior Lecturer, Early Childhood Education; Post Doctoral Fellow, Manna Institute, University of New England

This article is republished from The Conversation under a Creative Commons license. Read the original article.