Scratching the rash can pull scales off the skin and cause bleeding. As the rash spreads, bumpy red and silvery-scaled patches on the skin can develop.
Psoriasis can take hold anywhere on the body where there is skin. It is most often found on the knees and elbows, or on the scalp.
Types of psoriasis
There are several different types of psoriasis.
Plaque psoriasis is the most common type of psoriasis.
This is the most common form. According to the American Academy of Dermatology, 80 percent of the 7.5 million Americans with psoriasis have this form.
It usually produces red patches of plaque, with a silvery-white coating of scale.
It commonly appears on the scalp, the lower back, the elbows, and the knees. The patches can be sore and itchy, and they can get thicker if scratched.
Finger and toenails may also develop pits, or they may crumble or fall off.
Pustular psoriasis gives rise to painful, pus-filled bumps that are usually found on the palms of the hands and the soles of the feet. The skin surrounding the bumps is swollen and red.
When the bumps dry, they leave behind brown spots that may be covered with scale. Individuals with this condition may also develop a fever, chills, weak muscles, little appetite, extensive itching, and tiredness.
This form only appears in areas where skin is in contact with skin, or skin folds, including the armpits, behind the knees, the groin, the buttocks, the genitals, and under the breasts. The skin is very red, shiny, raw, and sore.
This form often develops after an illness, like strep throat.
Guttate psoriasis is identified by small red spots that form all over the body, most often on the chest, legs, and arms.
Found in about 10 percent of people with psoriasis, according to the National Psoriasis Foundation, guttate psoriasis can affect children and young adults, as well as those somewhat older.
Erythrodermic psoriasis is a rare and very serious condition. Individuals who develop symptoms should seek medical treatment immediately.
With the skin turning red, this condition looks like a burn over most or all the body. It is accompanied by intense pain and itching and a very rapid heartbeat.
Individuals may feel very hot or very cold, because it is not possible for the body to maintain a stable temperature.
Symptoms and complications
Psoriasis affects individuals in different ways, and it can take multiple forms, but people with all types of psoriasis typically have at least one of the following symptoms:
Guttate psoriasis can occur after a strep infection.
- Itchy, sore, or burning patches on the skin
- Red patches of skin, with silvery spots
- Small red spots on the skin
- Dry, cracked skin
- Changes in the nails
- Swollen joints.
The following factors can trigger a flare-up of psoriasis:
- Skin injury
- Medications such as lithium, beta-blockers, iodides, and antimalarials
- Cold temperatures
- Exposure to smoke
- Heavy use of alcohol.
Psoriasis is a life-long condition, but it can usually be managed effectively with over-the-counter treatments and medication.
However, it is also linked to the following complications:
- Psoriatic arthritis can develop in about 30 percent of people with psoriasis, and it often affects the joints closest to the fingernails and toenails
- Cardiovascular disease may be linked to severe cases of psoriasis
- Onychomycosis is a fungal infection experienced by around one third of those with psoriasis. It makes the nails grow thicker.
Psoriasis on the face can be challenging. The skin is very sensitive in this area, as are the eyes, so great care should be taken with treatment, even with mild cortisone creams.
Psoriasis may also develop on the eyes, in the ears, and around the mouth and nose.
When the hands and feet are affected, swelling, blisters, and cracking may follow. Prompt and cautious treatment is recommended. Phototherapy, combined with medication, may be an effective treatment.
With more severe cases, such as those involving pustular psoriasis, a biologic drug may be used.
About half of all individuals with psoriasis develop problems with their nails.
Nail psoriasis can cause the fingernails or toenails to crumble and break off.
These can include:
- Changes in the shape or color
- Thickening or developing holes
- Separation of the nail from the nail bed.
Psoriasis on the scalp ranges from the mild to the severe. Plaque lesions may grow beyond the boundary of the hairline to reach the ears, forehead, and the neck.
The National Psoriasis Foundation report that close to 50 percent of individuals living with psoriasis develop sores at this location.
Psoriasis in the genital area affects some of the body's most sensitive skin, so particular care needs to be taken with treatment.
This is usually caused by the inverse variety of psoriasis, so it is not scaly but it can result in tender, sensitive skin.
Psoriasis and other rashes
Eczema, another skin disorder that causes itching and discomfort, can be mistaken for psoriasis, but in a biopsy, skin affected by psoriasis will look thicker and redder than skin affected by eczema.
Shingles, a rash caused by the same virus that causes chicken pox, forms itchy, painful blisters on one side of the body. One notable difference with psoriasis is that the area where the rash develops will often feel uncomfortable before the rash appears.
Heat rash can cause itchy red blisters in skin folds. It may at times be confused with psoriasis. Physicians can make an appropriate diagnosis with a simple examination.
Other conditions that cause similar-looking rashes
The following conditions also resemble psoriasis:
- Lichen planus can appear on the skin as reddish bumps, or as white dots in the mouth
- Pityriasis rosea starts with a "herald patch" on the trunk, with smaller itchy patches spreading across the body in a shape frequently described as resembling a pine tree
- Ringworm, caused by a fungus, forms a circle-shaped itchy red rash
- Seborrheic dermatitis is an itchy, red skin condition usually found on the scalp and other oily areas of the body.
When to see a doctor
People should see a doctor if a skin rash lasts longer than a few days, if it interferes with their quality of life, or if there are other symptoms, such as a fever.
Various treatments are available for psoriasis. Treatment decisions are based on the form of psoriasis, the location of the rash, the severity, and its impact on the individual.
The most common approaches include:
- Exposure to sunlight
- Soaking with bath oils or tar solutions
- Using moisturizers to keep the skin from cracking
- Covering rash areas
- Lotions and creams, such as coal tar ointments, topical steroids, and compounds based on vitamin D or vitamin A
- Light therapy
Oral or Injected medications may be prescribed by a doctor.
Individuals sometimes use superglue to manage deep cracks in the feet due to psoriasis. Patients should check with a doctor first, to make sure this action would be safe, and that the patient is not allergic.