A dry scalp can cause dandruff, but the two conditions are distinct.
Dandruff causes the scalp to flake and may cause visible flakes on clothing or in the hair. In some cases, it is due to a fungal or other scalp infection. Dry scalp, by contrast, occurs when the scalp does not produce or hold enough moisture.
Understanding the difference between dandruff and a dry scalp can help with choosing the right treatment.
A dry scalp occurs when the scalp does not have enough oil for the skin to feel lubricated.
Like other forms of dry skin, this can cause itching, flaking, and irritation. It can also cause the hair to look dry, since oil from the scalp helps condition the hair.
People with dry skin are more prone to dry scalp. This means that many of the things that cause dry skin can also cause a dry scalp including:
- dry air, particularly during the winter months
- excessive washing
- skin conditions, such as eczema
The scalp, like the rest of the skin, sheds dead skin cells. Dandruff occurs when this process speeds up. Dandruff flakes are actually dead skin cells.
The faster the scalp sheds dead skin, the worse dandruff becomes. Some factors can alter the rate at which the skin sheds.
According to the American Academy of Dermatology, researchers do not fully understand what causes dandruff. Potential causes of dandruff include:
- fungal infections of the scalp
- oils secreted by the scalp
- sensitivity to substances, such as hair products
These three factors may work together to make some dandruff worse. For example, people with fungal scalp infections may develop worse dandruff if they have sensitive skin or a very oily scalp.
Most people have a fungus called Malassezia living on their scalp that does not cause any problems. However, in people with dandruff, this fungus causes irritation and flakes. This irritation may be due to the way the fungus interacts with other factors.
A 2016 study found a close relationship between the presence of certain scalp bacteria and dandruff.
People with a dry scalp may notice flakes shedding from their scalp. Unlike true dandruff flakes, however, the flakes associated with dry scalp tend to be smaller and whiter.
Dandruff flakes are larger and may be yellow-tinged or look oily. While both dandruff and dry scalp tend to come and go, dandruff that is due to a fungal infection is unlikely to get better without treatment. Dry scalp, however, may improve with less frequent shampooing.
Both conditions can make the scalp itchy and irritated. If symptoms are severe, people with either condition may scratch their scalp so frequently that it turns red or develops small sores.
Differences between dandruff and dry scalp
Most people find it difficult to tell the difference between dandruff and dry scalp, and it is also possible to have both dandruff and a dry scalp. In general, flakes are more likely to be dandruff:
- if the scalp feels oily
- when there is intense scalp itching even when the scalp does not feel dry
- if the hair looks greasy
Both dandruff and dry scalp can usually be managed at home. However, some scalp conditions can look like dandruff.
Scalp psoriasis, for example, causes redness, flakes, and itching but is caused by an autoimmune disorder. A form of severe dandruff called seborrheic dermatitis can cause intense, painful inflammation.
People should see a doctor for a flaky scalp:
- if there are other symptoms, such as redness or sores
- if home treatments do not work
- if there are open wounds on the head or face
People with autoimmune disorders and chronic illnesses should talk to their doctor before treating dandruff. Symptoms that resemble dandruff may be due to another condition, and a weakened immune system increases the chances that a scalp condition will quickly get worse.
Most cases of dandruff can easily be treated at home. People with dandruff should aim to shampoo their hair with anti-dandruff shampoo regularly. This can treat many underlying causes of dandruff, including minor fungal infections.
Most dandruff shampoos contain pyrithione, and many different types of anti-dandruff shampoo are available online.
Another option to treat dandruff is coal tar shampoo. However, this shampoo may change the color of light hair, so people with blonde or gray hair may prefer another option.
Dandruff shampoo can have a strong smell. Some people may wish to alternate between dandruff shampoo and traditional shampoo, or shampoo with a different shampoo immediately following treatment with dandruff shampoo.
People who prefer natural remedies, or who dislike the smell of dandruff shampoo, may wish to try tea tree oil shampoo. Tea tree oil has antimicrobial properties.
An old study found that a 5-percent tea tree oil shampoo could effectively treat dandruff without causing serious side effects. However, there is a lack of recent research to back this claim up.
People whose dandruff does not improve with home treatment should see a doctor. Identifying the cause of the dandruff — which could be a bacterial or fungal infection — can be helpful. Prescription-strength treatments usually clear up dandruff.
The idea that poor hygiene causes dandruff is a myth. Going long periods of time without shampooing, however, may make dandruff more visible.
As researchers do not fully understand what causes dandruff, it is unclear if it can be prevented.
In most people, dandruff is a chronic condition that tends to go away and then come back. While some people think that lifestyle changes improve their symptoms, there is little research on this topic.
It may be possible to prevent dry scalp by:
- using less irritating shampoos
- switching to a moisturizing shampoo
- shampooing the hair less frequently
- using a humidifier to keep the skin from getting dry
- drinking more water
Dandruff remains a mystery to many doctors who do not understand how a fungus that is harmless on one person's head can cause severe dandruff on another person. There are no guarantees with any dandruff treatment. There is no way to predict who will develop dandruff, or how severe it will be.
Both dandruff and dry scalp are annoying but not harmful. With home treatment, they usually go away.
People who do not see improvements with home treatment should consider that the problem might be something other than dandruff. Only a doctor can conclusively diagnose the cause of a flaky scalp.