• Skin bleaching may improve your appearance and correct hyperpigmentation by evening out dark patches, but the creams used to lighten your pigment can have a negative impact as well. The active ingredient in most skin bleaching products, hydroquinone, can cause side effects in some individuals. Always check with your doctor before using any bleaching product.
  
  

Irritation

• Skin bleaching creams and ointments can irritate the skin, causing a burning or stinging sensation and redness in some people. The risk of irritation increases if skin-bleaching products containing hydroquinone are used on skin that is sunburned, dry or chapped. Skin bleaching creams can also irritate open wounds if applied to the wound, which can slow healing times and increase the risk of infection.
  
  

Photosensitivity

• The hydroquinone in skin bleaching creams and ointments can increase your sensitivity to sunlight and artificial UV rays, such as the rays produced by sunlamps and tanning beds. People who use skin-bleaching products should avoid overexposure to the sun and artificial UV rays to prevent burning and skin damage. Wearing protective clothing and a sunscreen that is at minimum an SPF 15 when you will be exposed to UV rays is always important, but especially vital if you use skin-bleaching products.
  
  

Allergic Reaction

• According to WebMD, severe allergic reactions to hydroquinone are rare, but it is important to seek medical attention if you experience symptoms of an allergic reaction. People who are allergic to skin bleaching products may experience rash, swelling, dizziness and trouble breathing.
  
  

Skin Changes

• Some people who use skin bleaching products experience ochronosis, a condition that causes the skin to become dark and thick. Skin bleaching creams have also caused yellow and gray dome-shaped spots on the skin of African-American users, according to MedicineNet.com. Severe blisters and cracking of the skin are rare side effects, but they do occur in some patients. Patients experiencing these negative effects should stop using the product and consult their doctors.
  
  

Serious Effects

• Though hydroquinone has been identified as a possible carcinogen in rodent studies, it has not been proven to cause cancer in human trials, according to MedicineNet.com. The Food and Drug Administration proposed a ban on skin bleaching products containing hydroquinone on August 26, 2006 because of serious concerns. The drug has contributed to abnormal adrenal gland function and high levels of mercury in some patients. As of 2010, Japan, Australia and the European Union have banned products containing hydroquinone.