In short. The lesions that must be assessed rather than treated, the skin states that postpone both devices, and why refusing treatment is sometimes the right answer.
Key points
- Where a lesion needs a diagnosis, the appropriate step is usually removal and examination rather than laser treatment, because removal produces a diagnosis and light does not.
- A lesion that has been assessed and judged benign may still be treatable, and that is a clinical judgement made after the assessment rather than instead of it.
Both devices are effective at removing pigment, and there are situations where using either of them is the wrong decision. The most important of those concerns what the pigment is.
Lesions that are a diagnostic question
A mark that is new, that is changing in size, shape or colour, that has an irregular or indistinct border, that bleeds, itches, crusts or fails to heal is not a cosmetic problem first. It is a lesion that needs to be looked at, and often sampled, before anything is done to it. The reason is straightforward: a laser removes pigment without identifying it, and a lesion that has been treated cannot be assessed in the same way afterwards. Treating it delays a diagnosis and can hide what a clinician would have seen.
This is not a rare precaution. It is the single most important thing an assessment does with a pigmented lesion, and it is the reason a hospital setting is different from a commercial one for this particular question.
Removal and diagnosis
Where a lesion needs a diagnosis, the appropriate step is usually removal and examination rather than laser treatment, because removal produces a diagnosis and light does not. A lesion that has been assessed and judged benign may still be treatable, and that is a clinical judgement made after the assessment rather than instead of it.
Skin states that postpone treatment
Some skin states are reasons to defer rather than to choose between devices. Skin that is recently tanned or sunburnt is already responding to ultraviolet, and adding treatment raises the risk of a pigmentary change. Skin that is inflamed, infected, or being treated for another condition is not treated until it settles. A cold sore outbreak around the mouth is a reason to postpone, and a history of cold sores is usually treated preventively. Some medicines make the skin photosensitive, which changes how it responds to light.
Situations where neither device should be used
- A lesion that is new, changing, bleeding, itching or failing to heal. It is assessed, and often sampled, first.
- Reactive pigment such as melasma, or pigment that a previous laser has already made darker.
- Skin that is tanned, inflamed, infected or recently treated, or a patient taking a photosensitising medicine.
The commercial incentive points the other way, which is worth naming. A spot that can be lasered is a sale, and a spot that needs examining is an appointment that produces no treatment at all. That is why the order of the two steps matters more here than anywhere else in this comparison, and why a clinic that offers to laser a lesion nobody has examined is telling you something about how it makes decisions.
Being told that a spot should not be lasered is useful information, and it is sometimes the most valuable thing an assessment produces. Ask what should be done instead, and over what period, rather than treating the answer as a refusal.
Frequently asked questions
Which spots must be checked before any laser?
Any lesion that is new, changing in size, shape or colour, that has an irregular or indistinct border, that bleeds, itches or crusts, or that fails to heal. A lesion in those categories is a diagnostic question, and it is examined and often sampled before anything is done to it. Treating it first delays the answer and can obscure what a clinician would otherwise have seen.
Can I have a mole lasered for cosmetic reasons if it has been checked?
Sometimes, and often the answer is that it should be removed and examined rather than lasered, because removal gives a diagnosis and laser does not. A lesion that has been examined and judged benign may be treatable, and the decision turns on what it is, how it was assessed, and whether a sample is more appropriate. That is a clinical judgement rather than a patient preference.
Does a laser ever diagnose something?
No. A laser removes or lightens pigment; it does not tell anyone what the pigment was. A lesion that has been lasered without examination cannot be assessed afterwards in the same way, because the tissue that would have been looked at has been altered. That is the reason the examination comes first rather than as an optional step.
Risks & Limitations
- Pigmentary change in the treated area, darker in most cases and lighter in some, particularly in darker skin types and after recent sun exposure.
- Blistering, crusting or a burn if the settings do not match the skin, with a small risk of scarring.
- Frosting of a treated spot after a short-pulse treatment, which is expected rather than a complication and settles within hours to a day.
- Pinpoint bleeding and, with some settings, a bruise-like change after a very short pulse, taking a week or more to clear.
- A cold sore outbreak around the mouth after treatment in people who carry the virus.
- Pigment commonly darkens before it flakes away over the following days, and is judged once the area has settled.
- Pigment recurs. Sun-related freckling and sun spots return with further exposure and hormonal pigment returns most readily of all; only cleared tattoo ink does not.
- No outcome is guaranteed, and individual response varies with the lesion, the depth it sits at, the ink and the skin type.
When to Seek Care
- Blistering, crusting or a burn in the treated area — contact the treating team the same day.
- Rapidly increasing redness, swelling, pain or warmth, or discharge from the treated area.
- A fever, or a cold sore outbreak around the mouth after treatment.
- New or changing pigmentation in the treated area that is not settling as expected.
- A lesion anywhere on the skin that is new, changing in size, shape or colour, bleeding, itching or failing to heal — seek assessment rather than treatment.
- Difficulty breathing, or swelling of the lips, tongue or throat — seek emergency care immediately.
References & Further Reading
- American Academy of Dermatology Association (AAD) — patient information on laser and light-based treatment
- British Association of Dermatologists (BAD) — guidance on laser and light therapy
- National Institute for Health and Care Excellence (NICE, UK) — relevant guidance on skin lesions and referral
- Cochrane Library — systematic reviews in laser treatment of pigmented lesions and tattoos
This page is patient education, not medical advice, and it does not cite individual studies. Discuss your own case with a qualified clinician. To arrange an assessment at Chongqing West District Hospital, see Contact & Consultation.