If your blisters and rash don't go away after a week, or you become very uncomfortable, see your doctor. The doctor may prescribe oral medications, steroid creams, or light therapy to treat your spongiotic dermatitis. See your doctor if: you're so uncomfortable that it disrupts your sleep or ability to function daily, your skin is painful, self-care and home remedies haven't worked, or you suspect your skin is infected. A doctor may prescribe phototherapy (light therapy) to help heal spongiotic dermatitis. This very effective treatment can be as simple as limited sun exposure or may use artificial light, but it does not come without risks. Phototherapy exposes the skin to controlled amounts of natural sunlight or artificial ultraviolet A (UVA) and narrow band UVB. This treatment can be used alone with in conjunction with medications. Light exposure increases your risk for premature aging and skin cancer. If the itching or rash is not relieved by applying an over-the-counter topical corticosteroid, your doctor may prescribe either a stronger topical or oral corticosteroid such as prednisone. Oral steroids and strong topical steroids can have serious side effects when used long term. Follow your doctor's instructions and don't use these medications for longer than advised. Continue to moisturize your skin while using oral and topical corticosteroids. Not only will they keep your skin hydrated, but they will help prevent flare-ups when you discontinue use of the steroids. In case your blisters or rash area is infected, you can get an antibiotic to help make sure you remain healthy. Talk to your doctor if you see signs of infection, such as redness, swelling, warmth, or pus. The type of antibiotic your doctor prescribes may vary. Common antibiotics include erythromycin, penicillin, dicloxacillin, clindamycin, or doxycycline. When no other treatment works, get a calcineurin inhibitor cream that will help repair your skin. These drugs, which include tacrolimus and pimecrolimus, will help maintain normal skin, control itching, and reduce flares of spongiotic dermatitis. Calcineurin inhibitors directly affect the immune system and come with potential side effects including kidney problems, high blood pressure and headaches. Serious but rare side effects include an increased risk of certain cancers. These drugs are prescribed only when other treatments have failed and are approved for most people over the age of 2.
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One-sentence summary -- Visit your doctor if your condition worsens. Use light therapy. Use prescription corticosteroids. Get an antibiotic prescribed to combat infection. Use a calcineurin inhibitor cream to help repair the skin.

You will need a quiet, protected spot to keep the trapped cat before the clinic appointment and after the surgery. It should be a place where the temperature is mild (anesthesia renders them with less ability to regulate their body temperature), protects them from other animals. Make sure it is also quiet and free of disturbance. A spare bedroom or any dark area of your house would be appropriate. Closets or finished basements would also do nicely. To make sure the cat will be enthusiastic for the food you put out in the trap, as well as not overfed before undergoing surgery, skip a feeding. It might be hard, but resist the urge to put food out before you're ready to trap the cat. While you can withhold food, don't withhold water! Be sure to continue to give the feral cat water even the night before the attempted trapping. At the appropriate feeding-time (ideally 12-24 hours before the appointment), fold a lightweight cloth lengthwise and insert it to cover the wire bottom of the trap and the trip plate. Put about 2 tablespoons of canned cat food (or tuna, mackerel, or some other strong-smelling enticing food) at the very back of the trap. Set the trap and put it on a flat surface where it won't shift or tip prematurely. You can drizzle some juice or oil from the food in a zigzag pattern from the back of the trap towards the front if you want some extra attraction. Alternately, sprinkle a few grains of dry food leading into the back of the trap, but not too much. Consider putting an empty lid or cup in the cage to fill later with water after the cat's been trapped. Make sure the container doesn't have any sharp edges that the cat could get cut on. You can use a turkey baster to fill the lit from a comfortable distance. Don't leave the trap unattended but you don't have to spring into action immediately after the cat is trapped. It can, however, calm the cat down considerably to cover the trap immediately with a blanket or tarp after you see the trap has sprung effectively. Either way, bring the trap inside to your holding area as soon as you notice the cat's been trapped inside. It might thrash considerably, so be careful to keep your fingers out of the openings. The cat may whine and make otherwise terrible sounds that can be heartbreaking. Remember: You're doing the right thing.
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One-sentence summary --
Prepare your holding area before setting the trap. Withhold food for 12 hours before the appointment. Set the trap. Wait and watch.