Be suspicious if they complain of a persistently itchy head, or if you notice flecks of fine black powder or paler powder on pillows - signs of lice faeces and cast off lice skin. Lice eggs are easier to spot in dark hair, and can be hard to detect in fair hair. They're easier to see in a good light, especially sunlight. Although it's not always easy to distinguish between dandruff and lice eggs, white specks that are difficult to flick off the hair are more likely to be eggs. One way to check for these eggs is to comb the hair and part it into four, using clips or elastics.
Eggs are more likely to be behind and above the ears, the back of the neck and under fringes.
Follow the directions carefully. Use the shampoo in a well ventilated room. If you're pregnant, don't use the shampoo at all, either to wash your own hair or someone else's. Apply shampoo to all areas of the head, starting at the area close to the head and coating all hair from the root to the tip. Don't let any shampoo get into the eyes - get the person to shut their eyes and cover them with a cloth.