The Case

A mother presents to the Emergency Department at 1:30am stating that she was having a difficult time getting her three and a half year old son back to sleep. He kept crying and saying that his “butt hurt.” She tried to put him on the potty and she noticed that he had small white worms wriggling around his anus. This freaked her out. She promptly put him in the car and drove to the ED.

Warning: Sort of gross video of the crotch region of a patient with a pinworm

The Diagnosis

These are pinworms – the most common worm infection in the developed world. 20% of humans have likely had exposure to them. Even if you don’t see them on your exam a child with the above clinically presentation has pinworms. We can argue about the necessity of running to the ED at 1:30 AM. But that is a discussion for another day. The classic presentation is nocturnal perianal pruritus. This obviously impacts sleep. So reports estimate only ⅓ of patients have pruritus. There are case reports of patients who had abdominal pain but no itching. The worms may be found at the anal verge or in the vagina as well.

The disease is spread amongst humans, usually by fecal-oral contact, and it can take 4 to 8 weeks for the eggs to reach the anus, for the larvae to hatch and for patients to become symptomatic. Per Burkhart et al. “although transmission is often attributed to the ingestion of infective eggs by nail biting and inadequate hand washing, inhalation and ingestion of airborne eggs also occur.” Know that the eggs enter the human body though the mouth or nose and will get there either through the air, from hands/fingers, or on surfaces. The eggs are very hardy and can survive on bed linens, clothes or on toys and other objects. Pinworms don’t needSome patients are asymptomatic, others can continue to “reinfect” or auto infect themselves. School aged children are most at risk.

One makes the diagnosis ideally by seeing the eggs (under a microscope – they are tiny and transparent otherwise) and/or the organism itself (see video above). The worms themselves are about 1 centimeter in length and are white/pale-yellow in color. You can “catch” eggs on transparent adhesive tape to aid in the diagnosis. So, in a patient who suspects they have pinworms but doesn’t see them the tape method can aid in identification since you’ll at least get the eggs. You may need to have a few applications of tape though… Instruct patients to apply the tape to the perianal area each morning before bathing or defecating.

The Treatment

Treatment is with an anthelminthic agent, regardless of which one you choose (see below – get it), a single dose has a high cure rate, and a second dose given two weeks later is very close to 100%. Note, that there aren’t any really great comparative studies in children. All have the side effects of causing nausea, vomiting, abdominal pain and diarrhea.


Dosing: Oral, 400 mg as a single dose; repeat in 2 weeks. It comes in 200mg tablets.

Cost: >$400 per dose

Notes: Limited data in children <2 years, but probably safe.


Dosing: Oral, 100 mg as a single dose; repeat in 2 to 3 weeks if not cured with initial treatment. It comes in a chewable tablet.

Cost: Wholesale – $440 per dose

Notes: Limited data in children <2 years, but probably safe. After a long hiatus from the market it has recently entered production again under the trade name Emverm.

Pyrantel Pamoate

Dosing: Oral suspension, either do 11 mg/kg administered as a single dose (max: 1,000 mg) and repeat in two weeks, or…

11 to 16 kg: 125 mg
17 to 28 kg: 250 mg
29 to 39 kg: 375 mg
40 to 50 kg: 500 mg
51 to 62 kg: 625 mg
63 to 73 kg: 750 mg
74 to 84 kg: 875 mg
>84 kg: 1,000 mg

Cost: Generally <$15

Notes: Available in a number of “flavors,” most commonly “banana.”

It is recommended that you treat all household contacts. Also tell patients and families to wash personal items in hot water after each dose of medication (this includes bed linens!). Additionally recommend good hand hygiene, daily morning bathing, and daily underwear changes.

Final Thoughts

Remember that although this is a benign diagnosis it can be quite alarming to parents. They can also feel stigmatized – feeling as though this means that they are somehow “dirty.” Show some compassion and find a way to get treatment to all family members at home. This will go a long way in helping them go from “Oh my gosh butt worms!” to “OK, no big deal.”



Special thanks to Emergency Department Pharmacist Michelle Caruso, Pharm.D., BCPS for her help with this post.