A Mass General dermatologist shares tips about preventing, detecting and killing head lice, which can be found on one out of four elementary school students in the United States.

Head lice move fast. The bugs cannot fly, but they can crawl quickly from one scalp to another. Mass General dermatologist Mayra E. Lorenzo, MD, PhD, gives advice on preventing, detecting and treating an infestation.

What should people know about head lice? Are there any common misconceptions about them?

Lice can affect anyone! Avoid sharing items (like hats or helmets) that are in contact with the hair and scalp and avoid head-to-head contact. If lice infestation is reported at school, make sure to check your child’s hair daily.

How to Treat Head Lice

  1. Start with topical over-the-counter preparations formulated to kill lice (pediculicides). Look for products containing permetherin or pyrethrin with piperonlyl butoxide.
  2. Follow instructions on the product’s package. In general, apply product after shampoo and towel drying hair. Avoid using conditioner before treatment. Apply the product to the scalp and rinse in a sink or with a shower hose.
  3. Wet comb your hair daily for two weeks after the treatment, looking for lice and nits. Repeat the treatment in seven to 10 days.
  4. On the day of the treatment, launder clothing and linens use in the past two days by the person being treated.

One of the biggest misconceptions is thinking that if you have lice you are dirty or poorly groomed. The fact is, lice have no preference over a dirty or clean scalp. Lice are very fast movers! They will quickly crawl from one scalp to the next, but they can not fly. Close contact with the infested person or their personal items is needed for spread.

What ages and environments are most affected by head lice?

Head lice are found worldwide and affect humans of all ages, races and socioeconomic status. Lice most commonly affect children, and can be found on one out of four elementary school students in the United States.

Should people who aren’t in frequent, close contact with children worry about head lice?

Not as much. However, anyone can become infested with head lice if they come in close contact with an infested person. Children are most frequently affected.

What’s the first thing you should do if you think you have head lice?

Check your scalp! The best technique to detect active infestation is wet combing of hair:

  • Wet hair
  • Divide it into sections
  • Use a fine toothed comb or lice comb (teeth should be 0.2 mm apart) to slowly comb wet hair.

Adult lice are very small (3-4 mm in length, about the size of a sesame seed) and grey-white or tan-brown in color. Eggs or nits are seed shaped small pods that are cemented onto the hair. Once the egg hatches, the shell will remain attached to the hair until the hair is cut.

Most people experience severe itching of their scalp and neck and may even develop a rash on the scalp and neck.

Mayra Lorenzo, MD, PhD
Mayra Lorenzo, MD, PhD

There have been many reports this year about “super lice” that are treatment resistant. Are these a problem in our area? How should we treat them?

These report shows lice resistance in Massachusetts and many other states, however, this does not mean they are completely ineffective. The current recommendation is to treat first with an over-the-counter formulation.

Following additional precautions should be helpful. For example, wash all personal items and linens used for the two days previous to treatment, soak brushes and combs in hot water, vacuum the floor, carpet and furniture around where you sit or sleep. Do this at the time of treatment to avoid re-infestation and repeat the entire cycle seven to 10 days later. Most products do not kill eggs that have not hatched.

The second treatment seven to 10 days later is very important in killing any newly hatched lice before they lay new eggs. Check all close contacts daily for 15 days. If unsuccessful, there are prescription medications that will be effective as well and can be prescribed by a primary care physician.

To support the work of Dr. Lorenzo and her colleagues in the Department of Dermatology, please contact us.