It is a myth that going outside or to bed with wet hair puts you at risk of getting sick. However, damp environments usually provide a favorable environment for the growth of microorganisms such as bacteria, viruses or fungi. Hair tends to absorb water and retains it for some time by storing it in its shaft. This causes prolonged dampness or if slept on it, dampens the pillow. Therefore, damp hair increases the risk of developing a fungal or bacterial infection on the scalp, during summer due to warmer conditions or a viral infection during winter.

Reasons that might actually cause the cold:

The common idea that one can catch a cold or even pneumonia if they leave their hair wet and go outside or sleep is not correct. One cannot simply get sick from just wet hair. Wet hair can harbor higher amounts of microorganisms, such as a virus, and bacteria which might be the reason for the cold.

Moreover, colder air temperatures provide more comfortable environments for viral growth, such as the rhinovirus (the most common cause of the cold) and also make it easier for them to travel through the air.

There is some research suggesting during winter, people may have weaker immune systems due to the lack of sun and vitamin D. Another reason for catching a cold during winter may be due to the congregation inside the house which leads to the easy transmission of infections through the air from one person to another. That means gathering indoors might be the reason for your cold and not your hair or the cold weather that’s making you sick. 

Other risks associated with wet hair:

1. Hair thinning:  Hair naturally stretches by around 30% of its original length without damage when it is wet. However, prolonged wetness or sleeping on the hair may cause hair stretches between 30–70% that are irreversible. This leads to hair thinning.

 2. Feeling cold:  Studies have shown that on exposure to cool temperatures people’s heads significantly lost heat which ranged from 5-10 degrees Celsius (°C). This means wet hair may aggravate conditions like fever, and nose block or lead to uncomfortable sleep during winter.

3. Growth of fungus: Wet hair favours fungal growth. There have been scientific findings of the Malassezia fungal species in hair follicles. This fungus is responsible for causing skin conditions such as seborrheic dermatitis. Therefore wet hair that has not been dried or slept on overnight, may increase the risk of an overgrowth of this fungus leading to the frequent development of skin conditions.

4. Dandruff: Dryness during winter temperatures exacerbates dandruff. This worsens with prolonged wetness as wet hair releases heat. Another reason may be due to an imbalance in the number of bacteria and fungi caused by wet hair that may cause dandruff.

5. Hair breakage:  Hair loss can be due to many factors such as genetic and hormonal changes. However, wet hair weakens the hair follicles which can cause hair loss which can further damage the hair when sleeping on wet hair.

Skin conditions:  As wet hair harbors a wide range of bacteria and fungi, this can also affect skin conditions such as acne, eczema etc as these bacteria may grow in the pores or other parts of the skin. Therefore, if you are suffering from such conditions, it is safe to dry your hair to avoid the risk of aggravating conditions developing.

Conclusion:

In summary, we understand that sleeping and going out with wet hair is not the actual reason why a person catches a cold, especially during winter. The actual reason may be due to a communicable virus or the growth of viruses in damp hair. However, sleeping on wet hair may have some ill effects, such as hair breakage, yeast and fungal overgrowth or infection on the hair scalp or hair fall. It is therefore advisable to dry your hair and avoid practices that could damage your hair, including using tight bands, heat-based styling or a comb with narrow teeth.

You may also consult a dermatologist to find the best products available specifically for your hair concerns.