While not everyone with psoriasis has itching, most do
- some studies show around 80 percent of those with psoriasis suffer from itching and it is the most common complaint of those hospitalized for psoriasis. 
For some, the constant itchiness, even when plaques aren't present, is the most difficult part of the disease and the most debilitating. It is sometimes described as a burning, biting sensation or as if you are being bit by fire ants.
Constant itching is distracting, causing difficulty sleeping, problems concentrating, lowered sex drives and can lead to depression.  Even so, some dermatologists glaze over itchiness, focusing more on treating the lesions themselves. A serious concern, though, is that scratching can trigger psoriasis, the same way cuts or abrasions on the skin do. It can cause lesions to become red, swollen or infected. Many experience the "itch-scratch cycle" where scratching increases the inflammation, which increases the itching.
The following are tips on managing itchiness:
- Cool showers or tepid baths. You might find it more relaxing to take a long hot shower or bath, but hot water removes natural moisturizers from your skin and can increase itching.
- Avoid using perfumed or scented products. Look for products, including soaps, cleansers, shampoos, lotions, laundry detergent and household cleaners, that are marked "hypoallergenic" or "fragrance free." Perfumes and products with strong scents can worsen the itchiness.
- Take an "anti-itch" bath (remember warm, not hot water). Add oatmeal, epsom salts or dead sea salts to your bath water. (Check packaging for proper instructions on using these products)
- Use moisturizer frequently. Look for thick, greasy or cream type moisturizers and apply after you have patted your skin dry after a shower or bath (don't rub with a towel, pat dry to avoid irritating your skin.)
- Use over-the-counter antihistamines. These medications should help to relieve some of the itchiness. Non-drowsy formulas are available for daytime use.
- Apply anti-itch creams. There are a number of anti-itch products available, some contain corticosteroids, which should be used with care as long-term use may result in thinning of your skin. Other anti-itch creams include Gold Bond Medicated Anti-Itch Cream and Aveeno Overnight Itch Relief. Stronger products are available with a prescription.
- Apply ice-packs to your skin. This helps give you instant relief from itching and can help reduce swelling, but is usually a short-term solution.
- Apply capsaicin cream. Capsaicin is an ingredient derived from hot peppers and has been found to reduce itching. You may experience some burning or stinging when you first apply it.
- Use Bengay, Vicks VapoRun or Sarna Lotion. These products contain a topical anesthetic which deadens nerve cells, helping to reduce itching for several hours. Stronger products are available with a prescription.
If you find that these methods aren't working to help control or manage your itching, talk with your doctor about stronger medications or additional methods, such as light therapy, to reduce your psoriasis flare-ups and itching.
  "Treating Itch in Psoriasis," 2006, Aerlyn Dawn and Gil Yosipovitch, Dermatology Nursing