A skin biopsy is a procedure to remove cells or skin samples from your body for laboratory examination. A doctor uses a skin biopsy to diagnose skin conditions and remove abnormal tissue.

The three main types of skin biopsies are:

• Shave biopsy. A doctor uses a tool similar to a razor to remove a small section of the top layers of skin (epidermis and a portion of the dermis).
• Punch biopsy. A doctor uses a circular tool to remove a small core of skin, including deeper layers (epidermis, dermis and superficial fat).
• Excisional biopsy. A doctor uses a small knife (scalpel) to remove an entire lump or an area of abnormal skin, including a portion of normal skin down to or through the fatty layer of skin.

A skin biopsy is used to diagnose or help treat skin conditions and diseases, including:

• Actinic keratosis
• Bullous pemphigoid and other blistering skin disorders
• Inflammatory skin conditions
• Skin cancers, including basal cell carcinoma, squamous cell carcinoma and melanoma
• Skin infection, occasionally
• Skin tags
• Suspicious moles or other growths
• Warts

A skin biopsy is a generally safe procedure, but complications can occur, including:

• Bleeding
• Bruising
• Scarring
• Infection
• Allergic reaction to a topical antibiotic, if prescribed

Before the skin biopsy, tell your doctor if you:

• Are allergic to local anesthetics, topic antibiotics or antiseptics
• Have had reactions to tape
• Have been diagnosed with a bleeding disorder
• Have experienced excessive bleeding after other medical procedures
• Are taking blood-thinning medications, such as aspirin, aspiring-containing medications, warfarin (Jantoven) or heparin
• Are taking supplements or homeopathic medications — at times these can cause bleeding when taken with other medications
• Have a history of skin infections, such as impetigo

Depending on the location of the skin biopsy, you may be asked to undress and change into a clean gown. A doctor or nurse then cleans the area of the skin to be biopsied. Your skin may be marked to outline the biopsy area.

You then receive a medication (local anesthetic) to numb the biopsy site. This is usually given by injection with a thin needle. The numbing medication can cause a burning sensation in the skin for a few seconds. Afterward, you shouldn't feel any pain or discomfort during the skin biopsy. To make sure the anesthetic is working before the procedure begins, the doctor or nurse will prick your skin with a needle and ask you if you feel any sensation.

A skin biopsy typically takes about 15 minutes total, including the preparation time, dressing the wound and instructions for at-home care.

During the skin biopsy

What you can expect during your skin biopsy depends on the type of biopsy you'll undergo.

• For a shave biopsy, your doctor uses a sharp tool, a double-edged razor or a scalpel to cut the tissue. The depth of the cut varies. A shave biopsy causes bleeding. Pressure and a topical medication might be applied to stop bleeding.
• For a punch biopsy or an excisional biopsy, your doctor cuts into the top layer of fat beneath the skin. Stitches may be needed to close the wound. A bandage is then placed over the wound to protect it and prevent bleeding.

After the skin biopsy

Your doctor may instruct you to keep the bandage over the biopsy site until the next day. Occasionally, the biopsy site bleeds after you leave the doctor's office. This is more likely in people taking blood-thinning medications. If this occurs, apply direct pressure to the wound for 20 minutes, then look at it. If bleeding continues, apply pressure for another 20 minutes. If bleeding still continues after that, contact your doctor.

All biopsies cause a small scar. Some people develop a prominent, raised scar (keloid). The risk of this is increased when a biopsy is done on the neck or upper torso, such as the back or chest. Scars fade gradually. The scar's permanent color will be evident one or two years after the biopsy.

Avoid bumping the area or doing activities that stretch the skin. Stretching the skin could cause the wound to bleed or enlarge the scar. Don't soak in a bathtub, swimming pool or hot tub until your doctor says it's OK — usually about seven days after the procedure.

Healing of the wound can take several weeks, but is usually complete within two months. Wounds on the legs and feet tend to heal slower than those on other areas of the body.

Clean the biopsy site two times a day unless it's on your scalp — then clean it once a day. Follow these steps:

• Wash your hands with soap and water before touching the biopsy site.
• Wash the biopsy site with soap and water. If the biopsy site is on your scalp, use shampoo.
• Rinse the site well.
• Pat the site dry with a clean towel.
• After the area is dry, apply a thin layer of petroleum jelly (Vaseline). Use a new container of petroleum jelly the first time you do wound care. Use a new cotton swab each time you apply the petroleum jelly.
• Cover the site with an adhesive bandage (Band-Aid, Curad) for the first two or three days after the procedure.

Continue wound care until the stitches are removed or, if you don't have stitches, until the skin is healed.

If your wound is sore, ask your doctor if you can apply ice wrapped in a thin towel.

Your doctor sends the skin biopsy sample to a laboratory for testing. Results may take several days or longer, sometimes up to months, depending on the type of biopsy and the lab's procedures.

Your doctor may schedule an appointment to discuss the results. You might want to bring along a family member or friend to help you absorb all the information.

Write down questions that you want to ask your doctor, such as:

• Based on the results, what are my next steps?
• What kind of follow-up, if any, should I expect?
• Are there any factors that might have affected the results of this test and, therefore, may have altered the results?
• Will I need to repeat the test at some point?
• If the skin biopsy showed skin cancer, was all of the cancer removed, or will I need additional treatment?