When used on age spots, hydroquinone can cause mild topical irritation or more serious side effects including hives, respiratory trouble, and swelling of the tongue, mouth, face, and throat.

More Info: Since hydroquinone is a bleaching agent, it's not surprising that it can cause skin irritation. Mild irritation is somewhat normal and includes an itching, burning, or stinging sensation. However, you should consult a physician if irritation becomes severe.

The more serious side effects of hydroquinone - hives, breathing difficulty, and swelling - are signs of an allergic reaction. Get emergency medical assistance if you experience any of these side effects.

To reduce the chances of skin irritation, avoid using personal care products that strip the skin of its natural oils. Such products would include harsh soaps and shampoos, hair coloring and permanent chemicals, hot wax and other hair removers, and skin care products that contain alcohol or other ingredients that dry the skin.

Take these steps to further reduce the risk of hydroquinone side effects:

1. Avoid using additional medicated skin products without a doctor's guidance.
    
2. Stay out of the sun and artificial ultraviolet rays. If exposure is unavoidable, then wear protective clothing and a strong sunscreen.
   
   
3. Finally, if you do mix hydroquinone with benzoyl peroxide or another peroxide product, you might notice a temporary staining of your skin. This can typically be removed with a gentle soap and water.