Firm skin can stretch and snap back into place easily. When skin loses this ability, it starts to sag. Saggy skin can happen almost anywhere on the body. Common areas where you might see saggy skin include:

eyelids

jowls

chin

throat

upper arms

stomach

Loose skin is not a medical condition itself, but a sign of skin aging or other forms of skin damage. The areas most prone to skin sagging are your stomach, face, neck, arms, legs, and hips.

Flappy, hanging skin is accompanied by the following symptoms:

Fine lines and wrinkles, especially on the face
Loss of skin color, which makes it look increasingly pale or pigmented
Increased skin sensitivity

Aging
As skin ages, it loses two important proteins manufactured in the dermis — elastin and collagen.

As its name suggests, elastin gives skin elasticity. It provides firm skin with the ability to bounce back when stretched.

Collagen is produced by fibroblasts. When skin is taut and firm, it has collagen to thank. Collagen is comprised of tightly-constructed fibers, which help skin maintain its structure and firmness.

Both elastin and collagen production decline as people age. These two proteins can also become deteriorated by external factors over time, such as:

UV exposure
pollutants in the environment, including cigarette smoke
certain lifestyle factors, such as poor nutrition and drinking alcohol to excess
Too much sun exposure and not taking care of your skin or health can speed up the process of skin aging. This can make your skin look saggy and wrinkled at a younger age.

Weight loss
Carrying extra weight for an extended period of time can cause damage to the collagen and elastin fibers in your skin. This makes it harder for skin to snap back when you lose weight. If you lose a significant amount of weight of 100 pounds or more, significant amounts of saggy skin may result.

Sagging skin is more likely to occur when weight loss is rapid, such as after bariatric surgery. In some instances, these weight loss procedures may result in large amounts of sagging, drooping skin that hangs on the body.

Since younger skin bounces back more readily, your age at the time of weight loss can also play a role in how saggy your skin becomes.

Pregnancy
Acquiring some degree of saggy, loose skin is common after pregnancy. Women who carry multiples, such as twins or triplets, may see more sagging skin around the abdomen than those who carry one baby. Maternal age may also play a role.

Illness
There are a few medical conditions that are marked by saggy skin. One of these is a very rare subtype of cutaneous T-cell lymphoma, known as granulomatous slack skin.

People with this condition see a very gradual slackening of skin on the elbows and knees. Saggy skin caused by granulomatous slack skin does not typically respond well to treatment.

Ehlers-Danlos syndrome
Another condition that causes saggy skin is Ehlers-Danlos syndrome (EDS), a rare, connective tissue disorder that is inherited. People with EDS have a defect in collagen production that results in saggy, doughy skin, often on the face.