Dry hair: what causes it and what helps when it feels like straw

Dry hair is hair that has lost the thin natural oily layer on its surface, so it feels rough, looks dull and tangles easily. Most of it comes from everyday wear, such as frequent washing, heat, bleach, sun and dry winter air, and gentler habits help it feel softer again. If your hair turns dry suddenly and you have other symptoms, see a doctor.

What causes dry hair?

MedlinePlus, the medical encyclopedia of the US National Library of Medicine, defines dry hair as hair without enough moisture and oil to keep its normal shine and texture. On undamaged hair, a thin oily layer covers the outer surface and repels water. A review in the International Journal of Trichology (Gavazzoni Dias, 2015) lists what wears it away: rough washing, drying without protection, rubbing, sunlight and chemical treatments such as colouring. Without it, hair feels rough, tangles and loses its shine. Hair is not alive, so it cannot make this layer again.

The usual causes of dry hair:

• Washing too often, or with a harsh shampoo.
• Heat from hairdryers, straighteners and curling irons.
• Bleach, colour and perms, which change the hair surface for good.
• Sun, pool water and the sea. The American Academy of Dermatology (AAD) notes that UV light breaks down the proteins in hair and changes its colour.
• Rubbing from towels, brushes, pillows and scarves.
• Dry air, from the climate or from heating.

The ends are usually the driest part. They are the oldest part of your hair, and on long or curly hair the scalp's natural oil rarely reaches them. Dry hair frizzes easily too, because a rough surface takes up water unevenly; see what causes frizzy hair.

Why does my hair feel like straw?

Hair that feels like straw is usually more than dry. It is brittle: the outer layer is so worn that the hair snaps when you comb it, and the ends split. Dry, brittle hair is most common after bleaching, repeated colouring or years of straightening.

Be realistic about what care can do. The damage inside the hair is permanent, and a split end cannot be glued back together: only a trim removes it. What you can change is how your hair feels and how often it breaks from now on. Condition every time, use a leave-in on the lengths, turn the heat down, comb gently from the ends upwards and have the worst ends cut off. If you colour or bleach, the AAD suggests stretching the time between touch-ups to every 8 to 10 weeks. Our guide to split ends and how to prevent them covers the ends in more detail.

Does hard water cause dry hair?

Hard water carries more calcium and magnesium. Limescale on your kettle and shower head is a sign, and your water supplier can tell you how hard your water is. Many people blame it for dry hair, but the research is small and mixed:

• A 2013 study soaked hair from 15 volunteers in hard or distilled water for 10 minutes every other day for 30 days. It found no difference in strength or stretch (Srinivasan and colleagues, International Journal of Trichology).
• A 2016 microscope study by the same team found more minerals and a rougher, "ruffled" surface on hair treated with hard water (International Journal of Dermatology).
• A 2017 study of 20 volunteers found more magnesium on the hair after 3 weeks of hard water, but no clear surface damage under the microscope (Alahmmed and colleagues, Indian Journal of Dermatology, Venereology and Leprology).

So hard water does leave minerals on hair, which can make it feel coated and rough. On current evidence, though, it is unlikely to be the main reason your hair is dry. Conditioner after every wash helps most. If your hair feels coated, an occasional clarifying shampoo removes buildup. It is harsher than everyday shampoo, so use it rarely and always condition afterwards.

Why is dry hair worse in winter?

Cold outdoor air holds little water, and heating dries indoor air further. Hair gives water back to dry air. Textbook figures explained by chemist Michelle Wong show hair holding less than half as much water at 30% humidity as at 70%. She also notes that very dry air builds up static, which makes hair fly away. What helps in winter:

• Run a humidifier in your bedroom. The AAD suggests one for dry skin, and it keeps the air around your hair less dry too.
• Dry your hair before you go out. Wet hair is weaker and stretches more easily than dry hair.
• Wear long hair in a loose braid or tucked in, so collars and scarves rub it less.
• Smooth static flyaways with a drop of oil rubbed between your palms.

Dry scalp or dry hair?

They are different problems. Dry hair is about the lengths. Flakes and an itchy scalp are about the skin, and a common cause is dandruff, which the NHS describes as a common skin condition that is not harmful. The NHS suggests an anti-dandruff shampoo with ketoconazole, coal tar or salicylic acid for up to 4 weeks, and a GP visit if it does not improve. Oil on your lengths does nothing for the scalp. The AAD advises keeping leave-in products off the scalp, because they can cause buildup there.

When should you see a doctor about dry hair?

Most dry hair comes from how hair is treated. But MedlinePlus also lists medical causes, including an underactive thyroid or parathyroid gland, other hormone problems, malnutrition and eating disorders. The NHS lists dry skin, dry hair or hair loss among the symptoms of an underactive thyroid, along with tiredness, feeling cold and weight gain. See a doctor if your hair stays dry despite gentle care, if it breaks off or falls out, or if you have other unexplained symptoms. No hair oil changes shedding or hair loss.

What helps dry hair?

For most people, the answer is a gentler routine rather than more products:

1. Wash less often. MedlinePlus suggests once or twice a week for dry hair. The AAD says dry, curly or thick hair can be shampooed when needed, at least once every 2 to 3 weeks.
2. Shampoo the scalp only. Choose a gentle shampoo (MedlinePlus suggests sulphate-free) and let the foam rinse through the lengths.
3. Use warm, not hot, water. The AAD recommends warm water for dry skin, and your scalp is skin.
4. Condition every time, over the whole length if your hair is dry.
5. Blot, then comb gently. Wrap your hair in a towel or a cotton T-shirt, then use a wide-tooth comb.
6. Add a leave-in to damp hair, on the lengths and ends only. The AAD recommends leave-in conditioner for dry, brittle, curly and colour-treated hair.
7. Turn the heat down. Use a low or medium setting, with heat protection before you blow-dry or straighten.
8. Cover up outdoors. Wear a hat in the midday sun. Before a pool swim, the AAD suggests oil or a leave-in on your hair, and a rinse straight after.
9. Trim the driest ends regularly.

Does hair oil help dry hair?

It helps the part you can see and touch. A leave-in oil puts a thin layer back on the hair surface, so hair feels smoother and softer, looks shinier and is easier to comb. The International Journal of Trichology review describes how oils add shine and reduce friction, and how some, such as coconut oil, can get a little way into the hair. What oil cannot do is undo what bleach or heat has changed inside the hair. It also washes out, so it needs reapplying after you wash.

Use a small amount on damp, towel-dried hair. Start with the dry ends, which need it most, then run what is left on your hands through the lengths, and keep it off the roots. Ellips Hair Vitamin is a leave-in oil in single-use 1 ml capsules. Its silicones smooth the hair and protect it from heat up to 220 °C when applied before styling. Of its 4 formulas, Hair Treatment, with argan and jojoba oil, is made for thin to medium hair and helps prevent split ends and breakage. Smooth & Silky is for extra-dry, frizzy, medium to thick hair. For very fine hair, half a capsule on the ends is enough.

Frequently asked questions

Why is my hair so dry after washing?

Usually because of the shampoo, the water or the drying. A harsh shampoo can take off more oil than your lengths can spare, very hot water adds to it, and rubbing with a towel roughens the surface. Shampoo only your scalp, rinse with warm water, condition every time and blot instead of rubbing. If your water is hard and your hair feels coated, an occasional clarifying wash can help.

Why is my hair suddenly so dry?

Think about what has changed: a new shampoo, a colour or bleach, more heat styling, a holiday with sun, sea or pool water, or the start of the heating season. If nothing has changed, or the dryness comes with tiredness, feeling cold, weight gain or hair loss, see a doctor. The NHS lists dry hair among the symptoms of an underactive thyroid.

Can you fix hair that feels like straw?

Not completely. Hair that feels like straw is usually damaged inside, often by bleach or heat, and that damage is permanent. You can make it feel softer, look smoother and break less: condition every time, use a leave-in on damp lengths, turn the heat down and comb gently. Have the driest ends trimmed off, because they are the part that feels most like straw.

Should you put hair oil on wet or dry hair?

Damp hair is best for your main application. After washing, towel-dry your hair, work a small amount of oil through the lengths and ends, then dry and style as usual. The AAD gives the same advice for leave-in products: towel-dried, still damp hair. On dry hair, use just a drop rubbed between your palms, to smooth flyaways or rough ends during the day.