Brief Answer:
Please give additional information and post clear photographs.

Detailed Answer:
Hi.
Thanks for your query, albeit short and specific.
Noted the history and understood your concerns.
Wet feeling in anus for 18 months in spite of normal colonoscopy and sigmoidoscopy, no other symptoms can be due to the following:
Accumulation of sweat and inability to evaporate; with or without local dermatitis.

I would advise you the following in such a situation:
Clean the area with warm water and let it dry by cotton cloth or hair dryer.
Loose clothing.
Avoid hot and humid area.

Please give additional information for me to assist you better:
Work profile/ atmosphere in which you work and stay?
Please post clear and focused photo of the area after pulling buttocks apart as it helps sometimes for on-the-spot diagnosis.

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Brief Answer:
Get checked

Detailed Answer:
Thanks for your feedback.
Please check/get checked for dermatitis.
Post photos if possible.

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Brief Answer:
As detailed below.

Detailed Answer:
Thanks for the picture.
This shows local dermatitis around anus which is giving you wetness.
As advised above, use loose cloths, pure white cotton underwear.
Clean with plain water and make it dry as explained above.
You may apply Liquid povidone iodine locally to ward off any infection.
Avoid any ointments.
Consult your General Surgeon or a Dermatologist to get a proper diagnosis and get a prescription based medication. You need a valid prescription.
Take proper care and this can be cured.
Also take Multivitamins as these help in better healing.

I hope this answer helps you.
Please feel free to ask for any further relevant queries if you feel that there is any gap of communication.

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