Nearly every IPL device ships with a range of intensity levels, and nearly every user's first instinct is to figure out the highest setting they can tolerate and use that, on the theory that more energy means faster results. This isn't quite how it works, and using the wrong intensity for your actual skin tone and hair color is one of the more common ways people either get poor results or an avoidable skin reaction.
Intensity Is About Matching, Not Maximizing
IPL works by delivering enough energy to heat melanin in the hair follicle to the point of damaging the hair-producing structure, without delivering so much energy that surrounding skin tissue is also damaged. Melanin absorbs light energy regardless of where it is - in the hair follicle or in the surrounding skin's own pigment. This means the correct intensity setting is really a question of contrast: how much darker your hair is relative to your skin.
High contrast (dark hair, light skin) means most of the light energy that reaches the area will be absorbed efficiently by the hair follicle, with relatively little absorbed by the surrounding skin - so higher intensity settings are both effective and comparatively safe. Lower contrast (dark hair, darker skin; or light hair on any skin tone) means the skin itself is absorbing a meaningful share of the energy too, so pushing intensity higher increases the risk of surface skin heating - redness, burns, or (in rarer cases with darker skin) pigmentation changes - without necessarily improving hair reduction, since light or gray hair often lacks enough melanin to respond well at any intensity.
Using the Manufacturer's Skin Tone Chart
Most devices ship with a skin tone chart, typically based on the Fitzpatrick scale (Type I, very fair, always burns/never tans, through Type VI, deeply pigmented, never burns). This chart isn't a suggestion - it's derived from clinical testing of energy thresholds where the device remains both effective and safe for each tone. Devices with built-in skin tone sensors will often auto-select or restrict the intensity range based on a scan, but manual-setting devices require you to self-assess honestly, including on tanned skin, which shifts your effective category darker even if your baseline tone is lighter.
Starting Point and Progression
Regardless of what the chart's maximum recommended setting is for your tone, start at the lowest or second-lowest level for your first one to two sessions. This isn't overcaution for its own sake - it lets you observe how your specific skin responds (some people react more than the average person their tone would suggest) before committing to a higher setting across a full treatment area. If two sessions produce only mild, short-lived redness, increase by one level. Continue this gradual escalation until you either reach the chart's maximum for your tone or reach a level where redness persists longer than an hour or two, at which point you back off one level and stay there.
Different Areas May Need Different Settings
Skin thickness and sensitivity vary significantly by body area. The bikini line, underarms, and face (where approved) are thinner-skinned and more nerve-dense than calves or forearms, and often tolerate lower intensities more comfortably while still being effective, since hair follicles in these areas can also be more superficial. It's common and reasonable to run a device at a higher setting on legs than you do on the bikini line or underarms.
Signs You're Set Too High
Mild pinkness lasting under an hour is normal and expected. Warning signs that you should immediately drop your intensity include: redness lasting more than a few hours, swelling, small blisters, a sunburn-like stinging that persists, or any darkening/lightening of skin color in the treated patch over the following days. Any of these warrant stopping treatment on that area, letting skin fully recover, and resuming at a meaningfully lower setting - not the next level down.
Bottom Line
The right intensity setting is the lowest one that's still producing visible hair reduction over a full treatment cycle, not the highest one you can grit your teeth through. Use the manufacturer's tone-based chart as your ceiling, start low, escalate gradually based on your skin's actual response, and expect to run different areas of your body at different settings.