Summarize the following:
The citric acid in lemons does have natural lightening components. Unfortunately, the process will take some time. If you want to speed the process up, try using hydroquinone, kojic acid, alpha-hydroxy acids, or bearberry as lightening agents. Be warned, however: There are some risks associated with some of these products. One study showed that 1 out of every 4 skin lightening products made in Asia but sold in the U.S. contained mercury. When using lemon and other skin-lightening products, always use sunscreen and avoid unnecessary time in the sun.  Lemons and lemon juice can dry out skin, making it susceptible to sun damage. Lightening your skin with lemon juice will take a long time, so it's tempting to try to apply a mask or lemon juice every day. Try to stick to 3-4 applications every week. Lemon juice dries out the skin too much to apply every day. Some sources say that lemon juice kills the bacteria that produce acne while simultaneously clearing up acne scars. Lemon juice may do this, but it may also interfere with any topical treatments you are using for acne. Talk to your doctor about coupling your acne treatment with lemon juice. Much of what you put on your skin gets absorbed into your body. If you are using other ingredients besides lemon juice as a peel, a wash, a lotion, or a mask, use good judgment about whether you'd want it in your bloodstream.

Summary:
Lightening your skin with lemons does work, but will take time. Avoid exposure to sunlight. Try using lemon or lemon juice only every other day. Lemon juice may help with acne, but talk to your doctor about its effectiveness. Be aware of what products you put on your skin.