Sleep caps and minoxidil

Sleep cap for minoxidil: do you need one?

You don't need a sleep cap for minoxidil to work. A cap is for everything else. Once minoxidil is completely dry, a loose sleep cap holds what sheds from your hair overnight, so less of it ends up on the pillow you share with a partner, a child or a cat. The leaflet in the box puts it in that order: “Allow time for minoxidil topical solution 5% to dry completely before wearing a hat, or lying on a pillow, etc.”8 A cap goes on dry hair only, and it should never be tight.

Who a sleep cap helps, and who can skip it

You can probably skip it if

• You apply minoxidil 2 to 4 hours before bed and it is completely dry when you lie down.8
• You sleep alone and no pet sleeps on your bed.
• You wash your pillowcase often.

A cap makes sense if

• A cat or dog sleeps on your bed or your pillow. In a review of 211 poison-control cases, the most common route for cats was the owner's own use: licking the owner's skin or pillowcase, or a spill.1
• You share your bed with a partner or a child. In Spain, drug-safety officials traced 11 cases of infants growing excess body hair to a caregiver's minoxidil.3
• You sleep on your side or your face. Rogaine's guidance warns that product on your pillow can reach your face and grow hair where you don't want it.2
• You would rather wash one cap once a week than change your pillowcase every night.

Is it safe to sleep in a cap after minoxidil?

Yes, if the cap is loose and goes on over dry hair. The one documented problem case went the other way. A 28-year-old woman used 5% minoxidil twice a day, wore a wig all day and a tight cap all night, so her scalp was covered almost around the clock. More of the drug reached her bloodstream than it should have, and she grew unwanted hair on her face, arms and legs. It cleared after she stopped.4 A sleep cap for minoxidil should be the opposite: a loose dome, over dry hair, at night only. If you wear a wig or a tight hat during the day, ask your doctor before adding a cap at night.

What to look for in a sleep cap for minoxidil

1. Loose, not sealed.It should sit over your hair with room above the scalp and never press on the skin. Skip silicone caps and plastic wrap.
2. A layer liquid doesn't pass through.Satin and silk are kind to your hair, but they aren't waterproof, so residue can soak through to the pillow.
3. Made to be slept in.A deep cut and an elastic band at the hairline, so it is still on at 3 a.m. A shower cap is made for ten minutes.
4. Washable.The lining holds what sheds all week. It should go in the washing machine.
5. Your size.Long, thick or curly hair needs a bigger cut, or the cap ends up tight.

Can I wear a cap to bed after applying minoxidil?

Yes, once it is completely dry. The leaflet says to let the solution dry completely before wearing a hat or lying on a pillow, and that the nighttime application should happen 2 to 4 hours before bed.8 A cap on damp hair wipes part of your dose into the lining and holds the rest against your skin.

Should a minoxidil sleep cap be waterproof?

Waterproof in the middle, loose where it meets your hair. A waterproof middle layer keeps residue from passing through to the pillow. A soft lining and a loose fit keep the cap from sealing against your scalp. A cap that is waterproof and tight, like a silicone cap, is the wrong design.4

Do I wear the cap during the day too?

No. Night only. Your scalp needs uncovered hours, and the documented problem came from near-constant covering.4 In the morning, take it off and keep it in a closed bag, away from where your pet sits.