My baby has swollen and it showing a lot redness he is 10

Hi...thank you for uploading the images for my better understanding.
This is diaper dermatitis a common fungal infection very common in this age group and no specific cause can be attributed to this.
But common in diaper area due to the warmth and continuous contact.
I am sorry to say that the symptoms can be recurrent and persistent please.
The trick of the management is keeping the skin moist and never allowing it to be dry. For this oil massage and lotions like soft emollients will help.
You can use the mildest soap available.
Avoid diapers at home and use them only during outing.
At home put only cotton nappies with good aeration.
At night if you definitely need to put a diaper - please change it once in 4 hours please.
Topical barriers are applied with every diaper change; they should be applied thickly and can be covered with petroleum jelly to prevent sticking to the diaper.
Antifungal creams or ointments are applied to the diaper area beneath the barrier ointment two to three times a day until the rash has resolved.
Nystatin works well...but it's a prescription medication please.

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If you feel he is in real pain and agony please seek emergency care locally.