Frequently Asked Questions

Knowledge is power. And getting the facts about lice can be an important way to enhance your understanding during the treatment process. The following is a list of common questions that will provide you with the lice facts you need.

General head lice FAQs and information about lice

The most common symptom of lice infestation is itching. However, infestation may continue even after itching stops. In addition, infestation may be present even if there is no itching. Some children experience no symptoms.

Head lice are tiny, wingless insects that live on the human scalp. They are about as big as sesame seeds. Lice eggs are about the size of poppy seeds and are difficult to see because their color easily blends in with the infested child's hair. Eggs are laid near the root of the hair and are attached with a waterproof, glue-like substance that can't be washed or blown away.

Once lice have hatched from eggs, they leave empty eggshells behind called "nits". Nits vary in color—from yellowish-brown to white.

We have illustrations and details in the section called How to Recognize Lice on this site.

No. The types of lice that infest humans do not live on pets or other animals. There are other types of lice that live on animals, but these lice do not infest humans. If there is a concern that an animal may have lice, please refer to a vet for additional information. RID® is not approved for use on animals.

Head lice live approximately 40-50 days and go through 3 stages in their life cycle:

Egg Stage: The adult female louse lays the egg with a special glue that cements it to the hair shaft near the root. The eggs develop and hatch approximately 10 days later.

Nymph Stage: Once the louse hatches, it is called a nymph and is barely visible to the naked eye. The nymph cannot reproduce because it is not fully developed. After about 12 days, it becomes an adult.

Adult Stage: The adult louse can lay up to 4-10 eggs a day—starting another generation of lice. The adult stage lasts about 28 days.

The most common way of getting head lice is through head-to-head contact. Lice cannot fly or jump but they can crawl very quickly. Infestation can be spread by head-to-head contact with another infested person or by sharing personal items. To prevent infestation from spreading, DON'T allow head-to-head contact and DON'T share or borrow hair items (e.g., combs, headbands, etc.), headgear (e.g., hats, headphones, etc.), or other personal items.

Head lice seek warm temperatures, so they stay close to the scalp. Head lice are parasites that feed by piercing the scalp and sucking blood. The scalp often becomes itchy when the infested person has developed an allergic reaction to this feeding.

There are 3 kinds of lice which infest humans: (1) head lice, (2) pubic lice (crabs) and (3) body lice. The most commonly reported infestation is head lice.

General head lice treatment and prevention FAQs

Head lice can be passed from one child to another, usually by head-to-head contact. Also, make sure your child doesn't do the following:

  • Share or borrow combs, brushes, barrettes, hair ribbons, headbands, or other personal items
  • Share or borrow hats, sweaters, coats, scarves, helmets, headphones, pillows, or stuffed animals

Carefully inspect your child daily for at least 2 weeks. If you see lice or eggs, treat your child again by repeating Step 2 in the Lice Elimination process. Check other family members for head lice. If anyone in the family is infested, follow Step 1 and Step 2. Repeat Step 3 with any articles or items with which they have come into contact. Repeat Step 1 and Step 2 7 to 10 days after first applying the lice killing shampoo.

Head lice treatments, such as the RID® 1-2-3 Lice Elimination System, can be found in your favorite store in the First Aid or Shampoo aisle.

You may use the same comb on another family member who has lice as long as you wipe the teeth of the comb with a tissue after every combing.

To eliminate lice, the child or infested person(s) should be treated with a lice-killing shampoo, like RID® lice killing shampoo, which is 100% effective* when used as directed. After shampooing, combing is an essential step to remove lice, eggs, and nits.

According to the CDC, children diagnosed with live head lice can return to class after appropriate treatment has begun. Nits may persist after treatment, but successful treatment should kill crawling lice. However, check with your school to determine its policy.

*Reapplication required in 7 to 10 days for complete elimination.

RID® lice products FAQs and information

Wetting the hair can dilute the treatment. It is critical that you are careful about reading directions before using the product.

Rinse the Shampoo from the hair. Continue with the combing procedure in Step 2. Apply another treatment on DRY hair 24 hours later. This will be the Day One application. Re-apply treatment 7 to 10 days later to kill any newly hatched lice. Continue with the combing procedure after each application to remove dead lice, eggs, and nits.

Because a second treatment with lice killing shampoo and combing must be done in 7 to 10 days to kill any newly hatched lice, it is important to make sure that you have enough RID® lice killing shampoo and RID® Lice & Egg Comb-out Gel on hand to treat all affected family members.

Each RID® product has a purchase guideline table on its side panel that can assist you in determining how much product you may need, depending on hair length.

For Lice Killing Shampoo:
Hair Length Approx. amount for 1 Child/Adult
(ear length or
First Application: 1 oz.–2 oz.
Second Application: 1 oz.–2 oz.
Total: 2 oz.–4 oz.
(shoulder length)
First Application: 2 oz.–3 oz.
Second Application: 2 oz.–3 oz.
Total: 4 oz.–6 oz.
(past shoulder
First Application: 3 oz.–4 oz.
Second Application: 3 oz.–4 oz.
Total: 6 oz.–8 oz.
For Lice and Egg Comb-out Gel:
Hair Length Approx. amount for 1 Child/Adult
(ear length or
First Application: ½ Tube
Second Application: ½ Tube
Total: 1 Tube (2 oz.)
(shoulder length)
First Application: 1 Tube (2 oz.)
Second Application: 1 Tube (2 oz.)
Total: 2 Tubes (4 oz.)
(past shoulder
First Application: 1 Tube (2 oz.)
Second Application: 1 Tube (2 oz.)
Total: 2 Tubes (4 oz.)

RID® Lice Killing Shampoo is available in:
2 FL OZ (59 mL)
4 FL OZ (118 mL)
8 FL OZ (236 mL)

RID® Home Lice, Bed Bug & Dust Mite Spray is available in:
5 OZ (141.8 g)

RID® Complete Lice Elimination Kit contains:
4 FL OZ (118 mL) Shampoo
2 OZ (57 g) Lice & Egg Comb-Out Gel
3 OZ (85.1 g) Home Lice, Bedbug & Dust Mite Spray
RIDvantage® Lice Comb

All sizes of the Shampoo and the Complete Kit contain a removal comb and a color-coded detailed insert.

Yes, there is an expiration date on the product packaging.

Yes, vacate the room after treatment and ventilate before reoccupying.

When all directions have been followed for the 3-step lice elimination process, you should be free of lice after the day of your final application. To ensure that you are lice-free, it is critical that all steps be followed according to package directions. The full treatment requires 7 to 10 days.

Directions state to use RID® Lice Killing Shampoo on Day One and then 7 to 10 days later. However, it is important to check the hair continually and remove any nits or eggs that may have been missed in the initial combing process.

If you have recently used RID® and have lice again, please consult a doctor or pharmacist before using RID® again.

Most lice will die within, or shortly after, the ten-minute dosing. Lice are very sensitive to light and will move quickly when alive. If you observe lice crawling after treatment, they are probably affected and will die shortly. You should just comb them out of the hair.

Examples of some household items that should be cleaned are:

  • Home and auto upholstery
  • Rugs, carpeting
  • Mattresses, pillows, and pillowcases
  • Bed linens
  • Towels
  • Clothing
  • Coats, scarves, earmuffs, and gloves
  • Hats
  • Headbands
  • Baseball caps
  • Bike/Sports helmets
  • Headphones
  • Play mats
  • Stuffed animals, toys, dolls
  • Barrettes/hair ornaments

No. Although RID® provides complete lice elimination when used properly, it is designed for use in humans and is not approved for use on pets or any other animals. If you think your pet may have lice, be sure to contact your vet immediately.

Please see Step 2 of the proper Lice Treatment Steps.

While it is not necessary to use your own shampoo or conditioner after treatment, doing so will not interfere with RID®'s efficacy. RID® Lice Killing Shampoo will not leave an active chemical residue on the hair and its conditioning formula leaves your hair manageable.

No. RID® should not be used on an infant (under 2 years of age) without consulting a doctor. We suggest that you check your infant carefully for lice or eggs in his/her hair. If no lice or eggs are present, there is no need to treat the infant. If they are present, contact a physician before treating the infant.

Yes. You must treat pubic lice in a manner similar to that used for head lice. Please refer to the Pubic/Body Lice section for more information.

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