Dry hair: what are the causes?
Dull looking, coarse to the touch, a “straw-like” effect… Fortunately, dry or very dry hair can easily regain suppleness and shine with the right care and products. However, to take the most effective action, we must understand what causes dry hair. What are the internal and external factors responsible? How to recognise them? What steps should you take to nourish and hydrate dry hair? Let us find out.
Updated on , validated by our team of René Furterer experts.
What causes dry hair?
Naturally dry hair
One of the main causes of dry hair is genetics. Your hair may be dry (or even very dry) due to naturally low sebum production. Sebum is the primary component of the hydrolipidic film. It is produced by the sebaceous gland and transported through the sebaceous duct to the hair follicle, the scalp, and along the hair shaft.
Wavy, curly, and coily hair, whose texture is determined by genetics, is also dry by nature: sebum has difficulty reaching the lengths and ends, due to the shape of the curls (the tighter the curl, the drier the hair).
Finally, hair becomes dryer with age because sebum production decreases, preventing the hair shaft from being adequately lubricated.
What environmental factors cause dry hair?
Dry and/or damaged hair can be linked to environmental factors: the sun, heat, wind, cold, temperature variations and pollution can all make the hair fibre more fragile and drier.
Beware of seawater and swimming pool water. Faced with various external aggressions, the hair cuticles lift and the hair loses its suppleness and shine, becoming porous and increasingly dry.
Dry air can also impact hair hydration, especially in winter when houses are sometimes overheated.
The effects of excessive heat use
Using heated tools (such as hairdryers, straighteners, curlers) can weaken and dry out the hair fibre. Heat removes the natural oils and evaporates the moisture between the hair’s protective cuticles. Repeated use weakens the hair, dries it out, makes it brittle and prone to split ends.
When using one of these tools, use the lowest temperature (although it is not always possible to adjust the temperature) and apply a thermoprotective treatment to minimise damage. Pre-dry hair with a soft towel, microfiber if possible (gently dab, do not rub), and air-dry as much as possible.
The influence of diet on dry hair
An unbalanced diet can impact your overall health and hair health. Vitamin or trace element deficiencies promote dryness.
Which nutrients should you prioritise to nourish and strengthen dry hair?
- Essential fatty acids: omega-3 and omega-6 are essential for healthy hair. They provide nutrients needed by the hair follicles. A deficiency of essential fatty acids can lead to skin, scalp, and hair dryness. Omega-3s are found in oily fish (such as mackerel and sardines) and nuts. Omega-6s is found in most vegetable oils (grapeseed, sunflower, wheat germ, etc.).
- Vitamin A: particularly useful for dry hair, vitamin A stimulates sebum production. As a result, hair is better protected and hydrated. Deficiency, as well as overdose, of vitamin A can lead to dryness and hair loss. It is easily found in sweet potatoes, carrots, spinach, melon, liver, butter, eggs, etc.
- Vitamin B: Group B vitamins play an important role in hair health. They help in hair proteins, and keratin synthesis, and have nourishing properties. On the other hand, a B vitamins deficiency can result in dry, coarse, and brittle hair. They are found in various foods (brewer’s yeast, eggs, liver, tomatoes, etc.).
- Zinc: This trace element is involved in keratin synthesis. It contributes to hair shine and growth. A zinc deficiency can lead to thinning, brittle hair, and even hair loss. It is found in egg yolk and shellfish.
- Iron: another essential trace element, iron strengthens and nourishes hair. Vitamin C promotes iron absorption, while tea and coffee reduce it. Iron deficiency results in dry, thin, brittle hair and hair loss. It is found in red meat and lentils.
In addition to a varied, nutrient-rich diet, you can also consider taking food supplements.
Finally, do not neglect hydration: drink enough water throughout the day so that your hair can benefit from it.
Diseases and hormonal changes
In addition to the vitamin and trace element deficiencies mentioned earlier, certain health conditions may lead to dry hair. This includes hypothyroidism (insufficient production of thyroid hormones) or, more rarely, Cushing’s disease.
Hormonal fluctuations can also lead to hair dryness:
- Menopause: some women notice that their hair becomes duller and drier during this period. This is easily explained by the decrease of sebum production during menopause.
- Pregnancy: while most women experience improved hair quality during pregnancy, this period is synonymous with dry, dull, and brittle hair for others.
How to recognise dry hair
What happens to the hair fibre in dry hair?
It is important to understand what happens at a deeper level for the hair to become dry:
- The hydrolipidic film is damaged or may have disappeared. This essential film for healthy hair no longer plays its protective or hydration-regulating role.
- The hair cuticles lift. The cuticles overlap like roof tiles and form the outer layer of the hair shaft. However, they can lift, exposing the inner part of the hair. The moisture within the hair then evaporates far too quickly.
- Keratin is damaged at the heart of the hair. This fibrous protein is a key element of hair fibre, making up 95% of the shaft. When keratin chains break, the hair becomes dry, brittle and porous.
6 clear signs of dry hair
Dry hair has several recognisable characteristics:
- Coarse to the touch: when running your finger through your hair, it feels like straw.
- Difficult to detangle: dry hair easily forms knots and is unruly. Healthy hair is supple and can be detangled with a simple brush stroke. For dry hair, the operation can be painful.
- Dull appearance: dry hair lacks shine. This is because the cuticles of dry hair do not reflect light well.
- Brittle hair: a damaged hydrolipidic film and lifted cuticles make the dry hair brittle. Weakened hair breaks along the length. To test for brittleness, stretch a strand of hair from both ends, if it snaps quickly, it’s brittle.
- Split ends: dry hair often results in split ends. The ends are the oldest parts of the hair and therefore more fragile, especially when the cuticles have lifted.
- Frizz: dry hair can become frizzy, with small rebellious hairs sticking out from the rest, giving an unkept appearance. These hairs lack hydration and attempt to absorb moisture from the air. Frizz is more common in curly and coily hair but can affect all hair types.
What can be done about dry hair?
- To care for naturally dry hair, be gentle: adopt a hair routine that hydrates the hair, and avoid external aggressions that could intensify dryness.
- Protect your hair from environmental damage:
→ After a swim in the sea or a pool, do not forget to rinse your hair with clear water to get rid of both sea salt and chlorine.
→ In the sun, protect your hair with a scarf or hat, and use hair sunscreen.
→ In case of windy weather, tie your hair or wear a scarf or hat if your hair is short.
→ If your hair is exposed to pollution, use an anti-pollution treatment. This will leave a protective film of the hair and scalp, and prevent pollution particles from sticking to it.
→ In case of dry air (whether hot or cold), apply a leave-in hydrating treatment or oil to your lengths to prevent static electricity. - Colouring, bleaching, perming, and unsuitable treatments can worsen dryness. Replacing them with gentler alternatives, such as plant-based colouring is better.
- Beware of frequent shampooing as it removes the natural oils that protect and nourish the hair fibre. It is generally recommended to only wash dry hair once or twice a week. Choose a gentle shampoo to wash the hair without damaging it. Sulphates are surfactants commonly used in shampoos, but they can weaken and dry out the scalp. Opt for formulas based on natural active ingredients and select products designed for dry hair (treatments, masks, or styling spays), without forgetting to hydrate the scalp.
By adopting the right hair care routine, you can not only remedy dryness but also maintain the health and shine of your hair. Consistency and attention to detail in the care you give your hair are key.