Side effects of psoriasis medications vary depending on the type of medication. A common side effect of topical treatments is skin irritation, including pruritus (itching), burning and erythema (redness).

Topical retinoids, coal tar, psoralens and systemic methotrexate may increase susceptibility to sunburn. It is recommended that patients use a sunscreen with a sun protection factor (SPF) of at least 15 and avoid unnecessary sun exposure. Another common side effect is skin irritation including scaling, redness, dryness, erythema, burning sensations, itching and peeling skin.

Coal tar and anthralin may stain skin, clothing and hair. It is generally recommended to wear gloves when applying anthralin and to avoid contact with non-affected skin.

Topical corticosteroids may induce atrophy (degeneration) of the epidermis (top layer of skin) and thin the skin. They may also dilate blood vessels, cause stretch marks and lead to allergic contact dermatitis (skin inflammation caused by an allergic reaction to a substance making contact with the skin). When used over extended periods of time, corticosteroids can actually make psoriasis worse.

Vitamin D analogs may increase calcium levels in the blood, leading to hypercalcemia. In some cases, they may cause thinning of skin, dermatitis (inflammation of the skin) and severe skin irritation.

Oral retinoids are associated with numerous side effects, including severe birth defects or miscarriages when used during pregnancy. Women of reproductive age are required to use two separate, effective forms of birth control for one month before treatment begins, during the entire course of treatment and for months to years after treatment ends depending on the type. Pregnancy tests are typically performed every month during treatment. Other side effects may include:

• Dry, fragile skin and cheilitis (inflammation and redness of the lips)
• Nosebleeds
• Headaches
• Fatigue
• Nausea and vomiting
• Abdominal pain
• Lack of appetite
• Jaundice (yellowing of the skin and/or eyes)
• Dry eyes and mucous membranes
• Muscle and joint aches
• Liver damage
• Hair loss
  
• Photosensitivity
  
• Paronychia (inflammation of the nailfold area)

Methotrexate is linked to a large number of side effects, many of them serious. The most common adverse effects are hives (smooth, raised pink or white bumps that appear on or beneath the skin), irritation, rash, nausea, vomiting, and menstrual disorders. Serious side effects include arachnoiditis (inflammation of a certain membrane in the brain), nerve damage, seizures, kidney failure, leukopenia (not enough leukocytes in the blood), thrombocytopenia (not enough platelets in the blood), and liver damage. Other side effects include:

• Fever
• Malaise (feeling of being unwell)
• Dizziness
• Headache
• Drowsiness
• Blurred vision
• Diarrhea
• Abdominal pain
• Hair loss
• Joint and muscle pain

Other immunosuppressants may also have a large number of possible side effects. Cyclosporine may cause decreased kidney function, headache and high blood pressure. Mycophenolate may lead to gastrointestinal discomfort, headache and insomnia. Azathioprine may cause nausea, vomiting and fatigue and may cause the skin to bruise easily. Injected biological agents (e.g., etanercept, alefacept, efalizumab, infliximab) may cause a sore throat, dizziness and pain, inflammation and erythema at the injection site. Injectable immunosuppressants may also trigger flu-like symptoms.