It is targeted UVB.
Excimer delivers ultraviolet B at around 308 nm to selected patches.
Excimer Laser vs Punch Biopsy
Excimer Laser: A 308 nm ultraviolet B laser aimed at one patch of skin at a time. Used mainly for stubborn psoriasis plaques and for vitiligo. Because only the affected skin is treated, the rest of the body is spared the light.
Punch Biopsy: A small round blade takes a full-thickness core of skin, usually 3 or 4 millimeters across, closed with a stitch or two. It is the standard biopsy for rashes and for anything where the deeper layers matter.
Choose Excimer Laser if…
Choose for a few stubborn psoriasis plaques or vitiligo patches when you want light only where it's needed.
- A few stubborn plaques or patches
- Creams haven't been enough
- You can attend 2–3 times a week
Choose Punch Biopsy if…
Choose when a rash or growth needs a definite diagnosis that looking alone can't give.
- An unclear or stubborn rash
- A growth that might be cancer
- The deeper skin layers matter
Alternatives, not combined
Can you have both?
They serve different purposes. A biopsy confirms a diagnosis; excimer laser treats conditions like psoriasis or vitiligo.
Key differences
● Excimer Laser
● Punch Biopsy
DowntimeNone → 2+ weeks
None
1–2 weeks
PainMinimal → Needs anesthesia or sedation
Minimal
Mild
Results showImmediately → 3+ months
1–3 months
1–4 weeks
How long it lastsWeeks → Years or permanent
6–12 months
Years or permanent
Visits neededOne → Every few months
A longer series (4–6+)
One
Cost per visit$ → $$$$$
$
$
ReversibleYes, can be undone → No, permanent
No, fades slowly
No, permanent
What is it?
Excimer Laser
Punch Biopsy
What is it?
It treats psoriasis and vitiligo.
It is used for localized disease.
It is not eye surgery.
Dermatologic excimer differs from excimer eye procedures.
It is still phototherapy.
Light sensitivity, medicines and skin cancer history are reviewed.
It samples a cylinder of skin.
A circular blade removes a small core of tissue.
It reaches deeper layers.
It samples the epidermis, dermis and sometimes fat.
It investigates rashes and lesions.
It is a diagnostic procedure.
Melanoma needs a specific plan.
A partial sample may not characterize a whole mole.
What it treats
Evidence level
Excimer Laser
Punch Biopsy
Strong evidenceMost established uses
Psoriasis
Clears stubborn plaques.
Vitiligo
Restores color in small patches.
Suspicious Growths
Confirms a diagnosis.
Moderate evidenceSome supportive research
Scalp Psoriasis
Reaches the scalp through hair.
Psoriasis
Confirms an unclear rash.
Little evidence
Eczema
Other light therapies are preferred.
—
Not effective
—
Acne
Not needed for diagnosis.
Can make it worse
Melasma
UV light darkens patches.
—
Treatment areas
Treatment areas
Selected psoriasis or vitiligo patches; treatment follows the affected skin rather than a fixed body area.
The specific lesion, scar or affected patch determines the treatment site; there is no fixed body distribution.
Skin tones
Skin tone
● Excimer Laser
● Punch Biopsy
Lighter skin
Low risk
Possible small sunburn.
Low risk
A tiny scar.
Medium skin
Low risk
Surrounding skin may tan.
Low risk
A tiny scar.
Deeper skin
Some risk
Darkening around patches can make vitiligo edges stand out at first.
Some risk
Small raised or dark scar possible.
How it works
Excimer Laser
Punch Biopsy
How it works
Diagram explanation
UVB is aimed at a skin patch: A device delivers targeted 308 nm ultraviolet light. Immune activity is reduced: The light changes inflammatory activity in the treated skin. The patch may improve: Repeated treatment can help selected conditions such as psoriasis.
Schematic illustration. Technique and response vary. This explains a mechanism and does not specify treatment settings.
A site is selected and numbed: The clinician chooses an informative area to sample. A small skin core is taken: A circular blade samples epidermis and dermis. The laboratory examines it: The sample helps establish a diagnosis; the wound is cared for.
Schematic illustration. Technique and response vary. This explains a mechanism and does not specify treatment settings.
Before your treatment
Excimer Laser
Punch Biopsy
2–4 weeks before
2 weeks before: Sun and self-tanner: No sunburn and no self-tanner on the area for 2 weeks.
1 to 2 weeks before: Steroid cream: Stop the steroid cream a week or two before if you can.
Day of treatment
Excimer Laser
Punch Biopsy
Before you arrive
Clean skin and scale: Come with the area clean, with no makeup or thick creams.
Eating and clothes: On the scalp a small patch is trimmed short, not shaved bald.
Eating and clothes: Eat normally, take your usual medicines, wear clothes that make the site easy to reach.
Arrival & prep
For vitiligo: Photographs: Expect photographs at the start and every couple of months.
The area is looked at and often photographed.
The site is chosen, and not always the one you would pick — for a rash, usually fresh untreated skin rather than the oldest patch.
Treatment
You and the operator wear ultraviolet goggles.
The handpiece goes over the patch and light comes in bursts of a few seconds per spot. No smell, no noise beyond the machine, no feeling beyond mild warmth. Doses are written down each visit so the next can be adjusted. If the dose was too high you feel it hours later, like a small sunburn.
The skin is cleaned and stretched so the hole closes as a line, not a circle.
The punch is pressed and rotated, the core lifted out and cut free, then pressure stops the bleeding. One or two stitches and a dressing follow. You feel firm pressure and twisting, nothing sharp — say so if you do, and more anesthetic goes in.
Before you leave
Straight back to work.
A dressing for 24 hours, aftercare instructions, a stitch removal date, and a plan for how the result reaches you.
After your treatment
Excimer Laser
Punch Biopsy
First 24 hours
Day 1 to 2: Tenderness, deeper redness or mild peeling means the dose ran ahead of what your skin tolerated.
Days 1 to 3: From day two, wash with soap and water once a day, pat dry, apply plain petroleum jelly and re-cover.
Days 2–7
Not specified
Days 5 to 14: Face stitches come out at about 5 to 7 days, elsewhere at 10 to 14.
Weeks 2–4
Not specified
Weeks 2 onward: The line is pink or purple and can feel firm or lumpy.
Time to results
1–3 months
Lab report in 1–2 weeks
How long results last
Months; vitiligo color can be lasting
One-time test
After several sessions
Treated skin darkens.
Not specified
After weeks
Psoriasis plaques flatten and shed less.
Not specified
Risks
Risks
- Most of what happens is expected and mild
- A burn
- A cold sore
- Dark patches
- A new medicine
- Long term
- When to contact your provider
- Bleeding that will not stop
- Signs of infection
- The wound opening
- A stitch reaction
- A scar that is growing
- Numbness or tingling
Cost
Per session
Ask the office for a written estimate of the whole course before starting, and ask what happens to the price if a second area is added later.
In the US a punch biopsy usually produces two bills: the office fee, and a separate laboratory fee for reading the sample.
Insurance
Insurance in the US often covers targeted phototherapy for psoriasis and vitiligo, usually after prior authorization and often only once topical treatment has been tried.
Insurance normally covers it when there is a medical reason, subject to your deductible and copay.
Questions
Excimer Laser
Punch Biopsy
Individual Questions
How is this different from a narrowband UVB cabinet?
Only in where the light goes; the wavelength and biology are the same. The excimer treats defined patches at a higher dose each and leaves the rest untouched, which suits limited disease. A cabinet treats everything at once, which suits widespread disease.
Does it hurt?
Not much — a few seconds of warmth per spot. If the dose was pushed too far you feel it hours later, like a small sunburn.
How many sessions before I know if it is working?
For psoriasis, roughly 10 to 20. For vitiligo, 20 to 30 before judging at all. Stopping earlier is the most common reason people conclude it did not work for them.
Will the results last?
Nobody can promise that. Psoriasis plaques usually return after treatment stops. Vitiligo repigmentation often holds, especially on the face and when the disease is quiet, and is more likely to be lost while it is still active.
Is it safe on deeper skin tones?
It is used at every skin tone. The starting dose is higher, treated skin tends to tan, and the outcome to avoid is a burn, since dark marks from a burn last longer at deeper skin tones.
Does it cause skin cancer?
Ultraviolet exposure carries a theoretical long-term risk. Studies of narrowband UVB have not shown a clear increase, and the excimer exposes a fraction of the skin a cabinet does. Keep a record of your sessions and mention it at skin checks.
How big is a punch biopsy?
Usually 3 or 4 millimeters across — smaller than a pencil eraser. The skin is stretched first, so the round hole closes as a short straight line.
Does it hurt?
The numbing injection stings for a few seconds. After that you feel firm pressure and twisting, nothing sharp. Most people take nothing stronger than acetaminophen, on the first evening only.
Will I have stitches?
Usually one or two. On the face they come out at about 5 to 7 days, elsewhere at 10 to 14. Absorbable stitches dissolve on their own and are an option if getting back is hard.
Why did they biopsy a spot that looks fine instead of the worst patch?
For rashes, fresh untreated skin shows the diagnostic changes clearly, while the oldest patch has scratched, treated or healed skin over it. The site is chosen for what the pathologist needs to see.
What if the report does not name a disease?
Normal for rashes. The report describes a pattern that narrows the list, and the doctor combines it with what your skin looks like. Sometimes a second biopsy at a different stage settles it.
Will it leave a scar?
Yes — a small line or dot, a few millimeters. It stays pink for a couple of months, then fades. On deeper skin tones a brown mark is common for months, and raised scars are more likely on the chest, shoulders and upper back.
