How long the skin will be red after blue light therapy depends on how strong the treatment is and what skin type you have. But here is a general rule:
Typical Redness DurationMild At-Home Treatment (LED masks, ハンドヘルドデバイス):
0–2 hours (usually no lingering redness).
Professional treatment (at a dermatologist or clinic):
A few hours to 1 day (stronger devices may cause slight redness).
For sensitive skin/rosacea:
Up to 24–48 hours (if skin is reactive).
Why does it happen?
Blue light temporarily stresses bacteria and oil glands, causing mild inflammation.
Some devices also emit heat, which can increase redness.
How to Reduce Redness Faster
Apply Aloe Vera or a Soothing Serum (例えば, centella asiatica, niacinamide).
You can also use a cold compress for 5–10 minutes to calm the skin.
Avoid products with active ingredients like retinol, acids or vitamin C for 24 hours after treatment.
Moisturise and use SPF (if going outside).
When to WorryIf the redness lasts more than two days, or if it becomes swollen or burning, or looks like a sunburn, see your dermatologist (this is rare, but possible with overuse or sensitive skin).
