The most common type of skin manifestation, erythema nodosum, presents in up to 3% of UC patients and almost 8% in patients afflicted with Crohns disease. It develops as raised, tender red nodules usually appearing on the outer areas of the arms or legs, especially in the anterior tibial area (shins). The nodules have diameters that measure approximately 1–5 cm. Erythema nodosum is due to inflammation of the underlying subcutaneous tissue (panniculitis), and biopsy will display focal panniculitis (although is often unnecessary in diagnosis). In contrast to joint-related manifestations, erythema nodosum often occurs alongside intestinal disease. Thus, treatment of UC can often lead to resolution of skin nodules.A lesser common skin complication associated with UC, pyoderma gangrenosum, is typically more severe. One study discovered this skin manifestation in only 0.75% pf patients. Pyoderma gangrenosum is characterized by painful lesions or nodules that become ulcers which progressively grow. It often starts as many small raised red spots (papules) or pus-filled lesions (pustules) that are usually detected on lower extremities. The inner layer of the skin, or dermis, slowly undergoes necrosis (process of dying) causing the ulcerations that are typical of pyoderma gangrenosum. The ulcers are often filled with sterile pus-like material, so biopsy often displays an abscess that is sterile. Whereas erythema nodosum tends to correlate with the activity of the ulcerative colitis and often improves with treatment of the colonic inflammation, pyoderma gangrenosum may occur independently of UC disease activity. In some cases, pyoderma gangrenosum may require injection with corticosteroids.
Nesse, psychiatrist Isaac Marks, and evolutionary biologist George C. Williams have noted that people with systematically deficient responses to various adaptive phobias (e.g. arachnophobia, ophidiophobia, basophobia) are more temperamentally careless and more likely to receive unintentional injuries that are potentially fatal and have proposed that such deficient phobia should be classified as "hypophobia" due to its selfish genetic consequences.A 2001 study found that people could detect images of spiders among images of flowers and mushrooms more quickly than they could detect images of flowers or mushrooms among images of spiders. The researchers suggested that this was because fast response to spiders was more relevant to human evolution. Cultural
An alternative view is that the dangers, such as from spiders, are overrated and not sufficient to influence evolution. Instead, inheriting phobias would have restrictive and debilitating effects upon survival, rather than being an aid. For some communities such as in Papua New Guinea and Cambodia spiders are included in traditional foods. This suggests arachnophobia may, at least in part, be a cultural, rather than genetic trait.Stories about spiders in the media often contain errors and use sensationalistic vocabulary, which could contribute to the fear of spiders. Treatments
The fear of spiders can be treated by any of the general techniques suggested for specific phobias. The first line of treatment is systematic desensitization – also known as exposure therapy. Before engaging in systematic desensitization, it is common to train the individual with arachnophobia in relaxation techniques, which will help keep the patient calm.