Skin concerns
Uneven skin tone on the arms
Arms show a specific set of causes that faces do not. Where on the arm it appears usually tells you which one you have.
- Outer forearmCumulative sun, scattered flat marks
- Upper outer armRough bumps of keratosis pilaris
- Shoulders and backFaint scale suggests tinea versicolor
On this pageRead the map before treating5
Quick answer
The bottom line
Location is the shortcut. Patchy lighter marks on sun-exposed outer forearms are usually harmless sun-related changes, rough discoloured bumps on the upper outer arm are keratosis pilaris, and lighter or darker flat patches across the shoulders that scale slightly when scratched suggest tinea versicolor, which is treatable. Daily sun protection on the arms is the step that prevents further unevenness, and it is the one most people skip entirely. Give any treatment three months, and see someone about a single patch that grows, changes shape or has an irregular border.
At a glance
Three things worth remembering
- Sunscreen on the arms prevents further unevenness and is the step almost everyone skips.[1]
Section 01
Read the map before treating
A quick test for tinea versicolor is to scratch a patch gently with a fingernail: fine scale lifts that is not obvious when the skin is undisturbed. It also tends to become more noticeable in summer, because the surrounding skin tans and the affected patches do not.[3]
| Where | What it looks like | Likely cause |
|---|---|---|
| Outer forearm, back of hand | Scattered flat brown or pale marks | Cumulative sun exposure[1] |
| Upper outer arm | Rough bumps, red or brown at the base | Keratosis pilaris[2] |
| Shoulders, upper back, chest | Flat patches, lighter or darker, faint scale | Tinea versicolor[3] |
| Where a rash or spot healed | Flat brown marks in old sites | Post-inflammatory pigmentation[1][3] |
Section 02
The treatable one people miss
Tinea versicolor is an overgrowth of a yeast that lives on everyone. It is not contagious, not a hygiene failure, and it responds to antifungal treatment — selenium sulfide or ketoconazole applied to the area for the time the label specifies. Most people who have spent years assuming their shoulders were sun-mottled have never tried it.[3][4]
The catch is that clearing the yeast does not restore the colour quickly. Pigment can take several months to even out, and sun exposure during that window widens the contrast. Judge success by whether the faint scale and any itch have gone, not by the colour.[3][4]
Section 04
A plan that fits most people
- Start sunscreen on the arms daily, and keep it up during and after any treatment.[1]
- If the pattern fits tinea versicolor, treat it for the period the label specifies before assuming anything else.[4][3]
- If bumps are rough rather than flat, use a urea or lactic acid lotion and expect slow progress.[2]
- Change one thing at a time and give it three months. Arm skin is slower than facial skin.[2][1]
Section 05
What should be looked at
Uneven tone spread across an area is reassuring. A single spot that is growing, changing shape or colour, has an irregular or blurred border, or looks different from everything else on your arm should be examined rather than treated. Arms and hands take a lot of lifetime sun and are a common site for skin cancers.[5][1]
Also worth mentioning: patches that appeared quickly, are spreading, or came with itch or scaling that antifungal treatment did not settle. Several conditions produce similar patterns and need different treatment.[3][5]
Your next step
Turn this into a practical plan
Choose the guide that best matches what you see. Each one starts with what to try, how long to wait and when to get help.