When we think of serious health conditions, we often think of illnesses that wreak havoc on our internal organs. But with certain conditions and diseases, it’s not just about what lies beneath the surface. Some common illnesses can affect our physical looks as much as our internal parts.

Skin color

One of the most noticeable traits of skin is its color, making it obvious when a disease called vitiligo makes sections of skin lose their coloring. The result is patches that are lighter than those around them, including on the scalp and inside the mouth, and the changes can sometimes come with prematurely gray hair. Although some people with the disease report itching or pain on affected skin, the American Academy of Dermatology says it is not a life-threatening condition.

“But vitiligo can be life-altering. Some people develop low self-esteem. They may no longer want to hang out with friends or develop serious depression.” The usually lifelong skin condition affects the different races equally, and often hits before age 21, with the cells responsible for skin and hair color starting to die. Although the exact cause is unknown, the National Institute of Arthritis and Musculoskeletal and Skin Diseases notes that it could be an autoimmune disease, in which the “immune system mistakenly attacks some part of your own body.” The Vitiligo Research Foundation lists pop star Michael Jackson and comedian Graham Norton as famous people with the condition.

Pearly whites

Simply brushing and flossing may not be enough to keep teeth bright and healthy if you have diabetes. According to the National Institute of Dental and Craniofacial Research, people who are not adequately controlling their diabetes, specifically their blood glucose levels, “get gum disease more often and more severely than people whose diabetes is well controlled.” That may be because they are more susceptible to bacterial infection and less equipped to fight one off.

With the severe gum disease periodontitis, the gums recede and leave openings that germs and pus inhabit, infecting the mouth. If left untreated, it can “destroy the bone around your teeth,” leading to loose and lost teeth, the American Diabetes Association says. In turn, the poor dental health could make diabetes worse, the association explained: “Serious gum disease may have the potential to affect blood glucose control and contribute to the progression of diabetes.” Diabetes is also associated with fungus growing in the mouth, causing an infection called thrush.

Having a hunch

Most of us have seen someone walking down the street with a severe hunchback, and that can be a scary thing. But millions of Americans have the bone disease osteoporosis, one of the main causes of that physical alteration, called kyphosis. Osteoporosis can weaken the spinal bones “to the point that they crack and compress,” the Mayo Clinic says. The worst cases cause disabling pain and, because the spine curvature may compress the abdomen, can come with a decreased appetite.

Hair me out

Lots of health conditions can cause hair loss, such as thyroid problems or ringworm. It can also be a physical manifestation of the stress linked to anxiety disorders, which are common conditions. Those mental illnesses, which include generalized anxiety disorder and obsessive compulsive disorder, combined affect about 18 percent of the U.S. population, according to statistics from the Anxiety and Depression Association of America. In some cases of intense stress, the Mayo Clinic says, hair follicles can be forced into a resting phase, which means the hairs later fall out while the person is combing or washing them. Stress can also trigger alopecia, a condition that causes the immune system to attack the follicles.

Facial paralysis

Bell’s palsy symptoms can be as mild as twitching, but in more severe cases can cause weakness or even paralysis, usually on one side of the face. The National Institute of Neurological Disorders and Stroke says the condition, which hits about 40,000 Americans annually, particulary people between ages 15 and 60, occurs when a nerve that controls muscle movement in the face becomes swollen, inflamed or compressed, and its exact cause is unclear.

Because facial nerves control eyelid movement and facial expressions, those functions can be affected, causing an altered appearance, but the nerves have far more power than that — they are also involved with functioning in the tear and saliva glands, the ear and the tongue. That means other symptoms can include “drooping of the eyelid and corner of the mouth, drooling ... and excessive tearing in one eye.” Bell’s palsy can “lead to significant facial distortion.”