Hair chalking is the recent craze among teenagers that involves using a piece of Hairchalkcoloured pastel chalk on strands of hair then locking the colour in with straighteners.

It may be the newest teen trend in temporary hair colour, but the American Food and Drugs Agency warns it could have damaging adverse effects.

The problem is that many of the products are sold online and are not regulated. They may contain ingredients such as dyes or colorants, chemicals and preservatives that can cause allergies and adverse reaction on the scalp, head, eyes, and skin.

Concerns have also been raised that hair chalking could harm people with asthma if they inhale some of the ingredients.