It's recommended to apply at least 1 ounce (30 mL) of sunscreen to cover your entire body, which is about the amount that can fit in the palm of your hand. For the face and neck, a pea-sized amount is usually enough. It's also important to apply sunscreen generously and evenly, making sure to cover all exposed skin.
Applying too little sunscreen can result in inadequate protection from the sun's harmful UV rays, which can increase the risk of sunburn, skin damage, and skin cancer. Therefore, it's better to err on the side of applying more sunscreen rather than less.
As for whether there is such a thing as applying too much sunscreen, there is no evidence to suggest that over-applying sunscreen is harmful. However, excessive amounts of sunscreen can sometimes leave a white or greasy residue on the skin, which may not be aesthetically pleasing. It's also worth noting that the effectiveness of sunscreen may decrease over time, so it's important to reapply sunscreen at least every two hours, or more often if swimming or sweating.
Overall, applying a generous amount of sunscreen and reapplying regularly is the best way to ensure adequate protection from the sun's harmful rays.