Cantharidin
A liquid made from a blister beetle extract, painted onto molluscum bumps or warts in the office and washed off at home at a set time. It causes a small, controlled blister that lifts the lesion off. Putting it on does not hurt, which is why it suits young children. The blister that follows can.
Key facts
Treats
Molluscum or selected warts
Recovery
Blisters heal over 1–2 weeks
Treatment plan
Often 2–4 visits, 2–4 weeks apart
Typical cost
Product- and visit-dependent quote
What is it?
It is a blistering agent.
Cantharidin is applied to selected lesions by a clinician.
It treats molluscum.
YCANTH is approved in the US for molluscum from age two.
It is not a home product.
It is not a wart-removal liquid for home use.
It is toxic.
It must be kept away from the mouth and eyes.
Treatment areas
Cantharidin
The specific lesion, scar or affected patch determines the treatment site; there is no fixed body distribution.
Cantharidin
The specific lesion, scar or affected patch determines the treatment site; there is no fixed body distribution.
Skin tones
Lighter skin
Low risk
Pink marks fade.
Medium skin
Some risk
Temporary darker marks.
Deeper skin
Some risk
Darker or lighter marks may take months to fade.
How it works
Diagram explanation
Medicine is placed on the lesion: Cantharidin is applied to a carefully selected skin growth. A local blister forms: Superficial skin cells separate within the treated area. The area heals: The treated surface sheds and heals; more treatment may be needed.
Schematic illustration. Technique and response vary. This explains a mechanism and does not specify treatment settings.
Before your treatment
2–4 weeks before
Before you book: Plan ahead: Work out when the wash-off falls and whether you will be near soap and water.
The week before
A few days before: Actives: Skip salicylic acid, retinoids and strong exfoliants on the area.
Day of treatment
Before you arrive
Clean skin: Clean, dry skin.
Arrival & prep
The lesions are counted and the provider decides how many to treat today.
Treatment
Liquid is dabbed onto each bump with a wooden applicator, touching only the lesion, and air dries for a minute or two.
Some providers tape a wart afterward, which makes it stronger and changes the contact time, so ask. Several lesions take 5 to 15 minutes. You feel nothing during the visit; the discomfort comes hours later as the blister forms.
Before you leave
You go home with the liquid still on the skin.
After your treatment
First 24 hours
The spots look unchanged and you feel nothing.
Hours 4 to 24: A clear or cloudy blister rises over each treated bump.
Weeks 2–4
Weeks 1 to 2: The crust separates and takes the lesion with it, leaving pink, brown or pale new skin.
Time to results
1–2 weeks per treatment
How long results last
Treated bumps don't return
Risks
The blister is intended, not a complication. Blisters that are bigger, more painful or in the wrong place than planned nearly always trace back to contact time.
A blister much larger than expected
Especially one that is tense, painful or crosses a joint crease. Reduce the contact time or the number of lesions next visit.
Pain keeping a child awake
Worth a call. Painkillers and a dressing usually settle it, and the plan can be adjusted.
A ring of new bumps around a treated spot
Sometimes called ring warts. Harmless but frustrating, and a reason to change approach.
A lasting dark or pale patch
Common on deeper skin tones, usually temporary, and easier to treat early.
Redness spreading beyond the spot
Can be irritation from the liquid running, and it should be looked at.
Cost
Typical cost
Depends on the product used
Pricing
The answer depends on which product is used.
Insurance
The FDA-approved product is considerably more expensive, and what you pay depends on your insurance and how it is billed.
Alternatives
Watchful waiting
That molluscum clears on its own. Costs nothing, involves no blisters, and is a legitimate plan. The trade-off is months to a couple of years of visible bumps that can spread in the meantime.
Cryotherapy
Fast and done entirely in the office with no wash-off to manage. It is genuinely painful during and immediately after, which limits it in young children, and it leaves a pale mark more often on deeper skin tones.
Curettage
Scrapes the bumps off, often clearing many in one visit. Needs numbing cream and a child who can stay still, can be frightening, and carries a small risk of a scar at each site.
Potassium hydroxide solution
Applied at home, so no office visits, and cheaper. It stings, and overuse irritates the skin or leaves a mark.
Salicylic acid
For warts, weak for molluscum. Painless and cheap, done at home, but slow — weeks to months of daily use.
Imiquimod
Evidence does not support it for molluscum in children. Trials did not show a benefit, and it commonly irritates the skin, so it has largely fallen out of use for this.
Covering the bumps and not scratching
Molluscum spreads by scratching and by direct contact. Keeping bumps covered with clothing or a plaster, keeping nails short, and treating any eczema limits the spread while the immune system catches up.
Salicylic acid wart treatments
For warts. Liquids, gels and medicated plasters used daily for weeks to months. Painless, cheap, and the closest thing to a home version for warts. It is not a molluscum treatment.
Not sharing towels, flannels and baths
Simple household measures that reduce passing molluscum between siblings. Worth doing even during treatment.
Duct tape for warts
Trials have been mixed. Harmless and cheap, so reasonable to try alongside salicylic acid, but do not expect much on its own.
Questions
Does it hurt?
Not when it is applied — nothing sharp touches the skin and no numbing is needed, which is why it suits young children. Hours later a blister forms and can be sore or itchy for a day or two.
How long do I leave it on?
Exactly as long as you are told. Contact times differ between the compounded solution and the FDA-approved product, and between molluscum and warts. Longer just makes a bigger, more painful blister.
Will it leave a scar?
Usually not. The skin splits above the rebuilding layer, so most spots heal without a scar. What lasts weeks to months is a flat brown, pink or pale mark — pigment, not scar tissue. Picking early is what turns a mark into a scar.
Why does my child keep getting new bumps?
Because the virus is still there. Cantharidin removes the bumps it is painted on, but molluscum keeps making new ones until the immune system recognizes it, which takes months. Hence repeating every few weeks.
Can it be used on the face?
No. Cantharidin is not applied to the face, eyelids, or mucous membranes such as the lips or genital skin, because a blister there is painful and risky. Ask what suits those locations.
Do we have to treat molluscum at all?
No. It clears on its own. Treatment is usually chosen when bumps are spreading quickly, itching, sore, in an awkward place, or affecting a child's activities.
Related
Molluscum Contagiosum
Warts
Cryotherapy
Skin Tags
Salicylic Acid
Moles
Cantharidin vs Cryotherapy
Skin Tags vs Warts
Actinic Keratosis vs Warts
Ingrown Hairs vs Molluscum Contagiosum
Milia vs Molluscum Contagiosum
