She has a leak probably, one should feel no pain whatsoever if the ostomy appliance was applied correctly.
So she needs to stop eating/drinking and wait until the output subsides for an hour or so, remove it and take a shower and try again.
However if the itching is so bad that she wants to stick something hard under the wafer to scratch it it's likely a fungal infection just like athletes foot. Using antifungal foot powder in lieu of stoma powder covered by a spray skin protectant coating (30 seconds to dry after each coat) should work for this. It's okay to use the powder on non wound areas in this case but usually stoma powder is NOT to be used on healthy skin (wounds only) as it will dry it out and cause itching.
Now it could be dry skin itching that's the result of using alcohol, stoma powder on healthy skin (use only on wounds unless a fungal infection) or generally dry skin from other reasons. The fix for this is using oil free eye makeup remover as a adhesive remover and as a deep skin conditioner.
To resolve this when she removes the wafer and barrier adhesive is to use oil free eye makeup remover (instead of ostomy adhesive remover) available in the cosmetics isle of drug and supermarkets. Neutrogena is the best. Use no water and dry wipe the stoma of output at first until the skin is clean. Soak the oil free eye makeup remover around under the wafer area and it will moisturize the deep skin tissue and remove any stuck on adhesive. Then wash with plain soap and water gently just to remove it from the skin surface, after rinsing the skin should be squeaky clean when the finger is rubbed around the stoma. If not wash with the soap and water again.
Another reason could be she is using creams, oils or lubricants under the wafer which doesn't allow the barrier adhesive (paste of rings) to sufficiently bond to the skin thus output is getting underneath and causing the itching and burning.
Another factor is heat, the adhesives work better if the skin is warm or the adhesive is warm.
So try this next time
1: Oil free eye makeup remover to remove the wafer, scrape off any paste etc residue with a butter knife. Dry wipe any residue output. Use more oil free eye makeup remover to soak it in and remove residue adhesive and moisturize the deep skin tissue. Use no water during this process, dry wipe the stoma clean.
2: Wash area with plain soap and water to remove makeup remover from the surface of the skin. The finger test around the stoma should produce squeaky clean skin, it actually squeaks when rubbed.
3: Dry the area around the stoma with towel, then blow dryer (heats up the skin for better adhesion) then dry parts of toilet paper to soak up any residue moisture. Finger test by dragging finger around stoma to ensure it's very dry and not slippery.
4: A light dusting of antifungal foot powder on areas of the skin under the wafer that has been itching that's not a wound. Or any wounds gets a very light dusting of stoma powder. Dry brush off any excess, important or it won't bond. Coat the area with 1 or 2 light spray coatings of skin protectant and allow 30 seconds after each coat for it to dry. Finger test again and use a blow dryer if need be. If output gets on the skin then washing off with plain water (don't use spit it's salty and will burn) and drying well again should work for small output, larger and more consistent will require waiting in the shower rinsing it off until it's done and quieted down. It's important to water wash the output away or it will eat into the skin under the adhesive. Ensure area is extremely dry and warm (blow dryer) but not chapped skin.
5: Paste is better for uneven skin, bumps, dips and other irregularities around the stoma and rather active stomas as it quick seals unlike rings which slow melt. Rings are better for near perfect flat skin around the stoma with a slow active stoma. Rings require stretching and getting it tight around the stoma bonding to the skin first to insure it's sticking. Then the wafer (hole cut to fit almost tight around the stoma) and usually a heating pad on top to get it to melt and bond better to the skin. Paste just slap it on and go. But you may need three bead rings of paste instead of two. If you can when pressing the paste around the stoma is to get it to ooze out over the wafer hole just a tiny bit, it will deflect output away until the paste has adhered to the healthy skin better. Something one can't do with a ring unfortunately.
6: Many pastes have alcohol in it (Adapt) and this will cause wounds to itch and burn. Why I only use no sting pectin based pastes.(Bravda). Alcohol will dry out the skin oils and cause itching.
If you get proper barrier adhesion to the skin then the wounds will heal themselves in time. However if any pain or itching is felt that's consistent the wafer needs to be changed out quickly or else the wounds just get bigger and take longer to heal
Problem of course is if it's an illeostomy or colostomy then food and drink has to be maintained to ensure output doesn't clog, prolapse, cause pancaking or diarrhea of the stoma. Usually small sandwich sized meals more often throughout the 24 hours like about every 4-6 hours does the trick. However the food and drink type can cause issues as well, like alcohol, caffeine and salty foods.
So diet control is extremely important to maintain for consistent trouble free output that doesn't push the wafer off the skin or stoma output that is so much that it's impossible to get a good skin adhesion with your barrier adhesive.
Seeing an ostomy dietician and a stoma nurse can help a lot. You can read through my older posts here about diet control.
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