1. Incomplete coverage. It can be challenging to apply sunscreen evenly and cover all areas of the body, especially hard-to-reach places like the back or scalp. This can leave some areas vulnerable to sun exposure and potential sunburns.

1. Limited duration of effectiveness. Sunscreens typically have a specific duration of effectiveness, after which they may start to degrade or become less effective. This is why regular reapplication is recommended, especially after swimming, sweating, or prolonged sun exposure.

2. Potential for inadequate application. People may not apply enough sunscreen to achieve the stated SPF level of protection. Using insufficient amounts can significantly reduce the effectiveness of the sunscreen.

3. Chemical sensitivity or allergies. Some individuals may experience skin sensitivity or allergic reactions to certain chemical ingredients within sunscreen. Alternative options like physical sunscreens (containing zinc oxide or titanium dioxide) may be recommended in such cases.

4. Environmental impact. Some chemical sunscreen ingredients, such as oxybenzone or octinoxate, have been associated with potential harm to coral reefs and marine ecosystems when washed off during swimming or water activities. Using reef-safe or environmentally friendly sunscreens can help mitigate this issue.

It's important to note that despite these limitations, using sunscreen is still a crucial part of sun protection. However, it should be complemented with other sun safety measures, such as seeking shade, wearing protective clothing, and avoiding peak sun hours to maximize protection against harmful UV radiation.