White spots that become noticeable in summer are fairly common, and the cause matters because different conditions need different treatments. A dermatologist would usually consider several possibilities.
Common causes
Tinea versicolor: A very common superficial yeast infection. It produces lighter or darker patches, often on the chest, back, shoulders, or neck. They become more obvious after tanning because the affected skin doesn’t tan normally. Mild scaling may be present.
Pityriasis alba: Pale, slightly dry patches, usually on the face, especially in children and young adults. Dry skin and eczema can contribute.
Vitiligo: Causes sharply defined patches of depigmented skin. It can occur anywhere and sometimes gradually expands. Hair within the affected area can also turn white.
Post-inflammatory hypopigmentation: Skin can temporarily become lighter after eczema, irritation, a rash, or an injury.
Sun-related changes: Repeated sun exposure can make existing differences in pigmentation much more noticeable.
What can you do?
If the spots are scaly or mainly on the trunk, a clinician may suspect tinea versicolor and recommend an antifungal treatment such as ketoconazole or selenium sulfide. The color can take weeks or months to return to normal even after the yeast has been treated.
If the patches are smooth, completely white, sharply bordered, spreading, or recurring, it’s better to have a dermatologist examine them rather than trying antifungal medication on your own.
Regardless of the cause, broad-spectrum sunscreen (SPF 30+) helps prevent tanning from increasing the contrast between the spots and surrounding skin.
If you describe where the white spots are, whether they’re itchy/scaly, how long you’ve had them, and whether they disappear in winter, I can help narrow down the possibilities.
