In short. Melasma that may worsen, undiagnosed lesions, light-sensitising medicines, hormonal or deep pigment, and expectations no light can meet: when light is wrong.
Key points
- A lesion that is new, changing in size, shape or colour, bleeding, itching or failing to heal is examined before anything is treated.
- Light treatment of an unidentified lesion delays a diagnosis.
- No light source diagnoses anything, and a clinic that treats a changing mole as a cosmetic problem has skipped the step that mattered.
Both light sources are useful within limits, and there are situations outside those limits entirely. In those, the correct advice is not a different device, a different setting or a longer course. It is that light is the wrong tool for what is on the skin.
Pigment that light can make worse
Melasma is the clearest example: symmetrical, sun-sensitive, often hormonal and reactive. Inflammation makes it darker and more stubborn, and light treatment is a controlled form of inflammation. An aggressive course on melasma can leave the patient worse than she arrived, and the worsening can take months to settle. It is managed mainly with sun protection and topical treatment, and where light is used at all it is used cautiously, at low settings, by someone who has said it may not help. Other reactive pigment, and pigment that previous light treatment has already darkened, falls into the same category.
Skin that is not ready
Active infection, broken or inflamed skin, a cold sore outbreak, or significant recent sun exposure all mean treatment is deferred rather than adjusted. Light delivered to skin that is healing or inflamed adds a second injury to the first. Some medicines and some medical conditions increase sensitivity to light — certain antibiotics, some treatments for blood pressure or heart rhythm, some hormonal treatments, and a group of conditions in which skin reacts abnormally to ultraviolet. This is not a list to self-check against; it is why the medical history matters, and any medicine you take should be declared before a light treatment is planned.
When the answer is a diagnosis, not a device
A lesion that is new, changing in size, shape or colour, bleeding, itching or failing to heal is examined before anything is treated. Light treatment of an unidentified lesion delays a diagnosis. No light source diagnoses anything, and a clinic that treats a changing mole as a cosmetic problem has skipped the step that mattered.
Pigment that is hormonal or deep
Pigment driven by hormones, and pigment sitting deeper in the skin, respond poorly to light and often recur. Hormonal pigment belongs to a plan built around protection and topical treatment. Deep pigment may be reachable by very short pulses but can also darken paradoxically, and that risk is highest in the skin types where such pigment is most common.
Expectations no light source can meet
- Removing a lesion rather than lightening it. Light changes colour; it does not excise. Anything that needs to be gone is a surgical or diagnostic question.
- Permanence without maintenance. Neither source stops the process that produced the problem, and no course keeps pigment or redness away for good.
- A different skin type, smaller pores, or tighter skin. Light acts on colour and, to a small degree, on the surface. Structure and texture are treated another way.
Saying no is part of the assessment rather than an absence of one. A clinician who declines to treat a lesion, defers a course after sun exposure, or refuses an aggressive plan for melasma is applying the judgement that makes light treatment safe when it is appropriate. Treating everything because the equipment is available is how people end up worse than they started.
Frequently asked questions
When is light treatment the wrong answer?
When the pigment is reactive and likely to worsen, when the skin is not ready because of infection, inflammation or recent sun exposure, when a medicine or condition increases light sensitivity, when the lesion has not been identified, or when the expectation is something light cannot deliver. In each of those, the correct advice is not a different device or a longer course. It is that light is the wrong tool for what is on the skin.
Why is melasma treated differently from other pigment?
Because it is reactive. Melasma is symmetrical, sun-sensitive and often hormonal, and inflammation makes it darker and more stubborn. Light treatment is a controlled form of inflammation, so an aggressive course can leave the skin worse than it started, and the worsening can take months to settle. It is managed mainly with sun protection and topical treatment, and where light is used at all it is used cautiously, at low settings, with the possibility of worsening stated in advance.
Which medicines increase light sensitivity?
Several classes do, including some antibiotics, some treatments for blood pressure or heart rhythm, and some hormonal treatments, and a group of medical conditions make skin react abnormally to ultraviolet. This is deliberately described by class rather than by name, because it is not a list to self-check against. What matters is that every medicine you take is declared before a light treatment is planned, however unrelated it seems.
Risks & Limitations
- Redness, warmth and swelling for hours to a few days after either light source; pigment often darkens before it flakes away over the following week.
- Purpura — a bruise-like change — with some picosecond wavelengths, taking a week or more to clear.
- 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, and a small risk of scarring with either light source.
- A cold sore outbreak around the mouth after treatment in people who carry the virus.
- Results are not permanent. Sun-related pigment and redness recur, maintenance sessions are normal, and no course makes the change permanent.
- A lesion that has not been identified should be assessed, and in some cases sampled, before any light treatment; light does not diagnose.
- No outcome is guaranteed, and individual response varies with the lesion, the depth it sits at 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 and light treatment of pigmented and vascular lesions
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.