Easily rid even the worst cases of poison ivy/oak/sumac with household items and manage it with a few store-bought items. An inexpensive alternative to buying over the counter scrubs, washes, ointments, etc.
Wash affected area with Dawn Antibacterial Liquid Dish Soap & Water. There is no need to scrub on the skin with this, just gently dab and slightly lather on skin. This will remove any excess oils and helps dry out the urushiol oil that irritates the skin and causes the rash to itch.
Spray Band-Aid Calamine Spray on the affected area as needed. This stuff really works! I spent TONS of money trying to find something that helped, since I had it for over a month. This product is tried and true! Available at Wal-Mart, CVS, and other places. It has Lanacaine in it which numbs the rash and calamine lotion to help protect the area. You can use this at ANY point in time.
Get out the louffa and Clorox Bleach and get ready! I've also used a regular dish rag for this step. This step is going to sting a bit, but if you're willing to deal with a few minutes of pain for relief from itching and quickness of drying up the rash, then I would highly recommend this. Dilute the Clorox Bleach in some water, you can use a 1:1 ratio (1/2 Bleach, 1/2 Water), but I've been known to use 2:1 ratio with more bleach and less water. Dip the louffa or wash rag in the mixture and scrub on skin. This will open up the rash and let the oils drain as the bleach disinfects and dries up the rash. I've only had to do this process one time because I scrubbed until it burned.
Your skin will probably be irritated by the time you're done with the bleach and feel very tight, especially after washing with the dish soap. I usually spray the Band-Aid spray back on the affected area, let it dry, then rub Aveeno lotion on the affected area so the skin does not dry out. I found out the hard way that I was treating poison ivy when it was really leftover dry skin that was itching, so it's important to hydrate the skin to remove the itch as well. They usually have Aveeno moisturizing lotion (No Fragrance) at any store and sometimes special Aveeno lotions in the aisles where you find other poison ivy remedies (Aveeno Anti-Itch Lotion).
Take luke-warm to cold showers to ease irritation. Warm water may provide instant relief but irritates the skin more and may open rash and let it spread. I took cold showers for a week during this process, and it really helped. Be sure to wash the affected area using the Dawn liquid dish soap still to help dry oozing and rash (even in the shower!) instead of bar soap or body wash. The dish soap can be used several times a day whenever you start to itch. It helps for a few hours (I've experienced up to 6 hours of relief with one wash). Just be sure to keep lotion handy just in case because the dish soap will dry skin out (it's how it cleans dishes so well - the degreasing formula!) You may use the Aveeno body wash (Skin Relief formula) as well if desired, but not required. It kept my skin more hydrated than other body washes during the healing process.
Keep the Band-Aid Calamine Spray handy in vehicle, purse, or other. It really really works! It was the MOST helpful thing in the poison ivy treatment aisle. It costs about $4.00 and lasts for a while, depending on size of rash. Remember to hydrate the skin with lotion. I like the Aveeno because it has oatmeal-based ingredients and no fragrance to harm the skin. It's very hydrating, soothing, and relatively inexpensive. (About $5.00?) Remember to use the liquid dish soap EVERY time you wash the rash. It REALLY dries up the area and soothes irritation. I would much rather experience a little bit of pain to help relieve the irritating itch of poison ivy/oak/sumac. I realize that Clorox bleach may be a bit extreme, but it really works. It disinfects and dries up the rash quicker than any scrub or ointment I've used before. Trust me, I had the steroid shots, pills, hydrocortizone creams and ointments and nothing has worked better than these steps. You may mix up the steps to your own convenience, they are pretty versatile. Just be sure to keep the affected area clean and as dry as possible.
Do NOT under ANY circumstance wrap/cover up affected area. Air flow increases the healing process. By covering the area you're allowing the oils to penetrate back into the skin causing more irritation. If you're allergic to any of the products mentioned, you may try to substitute. I've just specifically used those common items and they really work. Stay out of sunlamps and sunlight and warm areas - they will only irritate the skin more. Don't itch! It can get in your nails and spread. I can't caution you enough on this because it's so tempting. Use the remedies above instead and I promise they will help - you won't need to itch!