Hello,
Dermol 500 lotion contains four main ingredients: liquid paraffin, isopropyl myristate, benzalkonium chloride and chlorhexidine hydrochloride. Liquid paraffin has moisturizing properties and benzalkonium chloride and chlorhexidine hydrochloride have antiseptic properties. It is often used for dry and itchy skin conditions such as eczema and dermatitis.
If you are having such symptoms in the anal area then it can be due to chafing, eczema or fungal infection also. For these symptoms, do not use any cosmetic products at the sites. You can apply some calamine lotion at the rash as it will help in soothing the skin. Also wear cotton undergarments. Application of mild corticosteroid cream and oral antiinflammatories like ibuprofen/acetaminophen are also helpful. If the symptoms are severe then it will be best to consult a dermatologist.
I hope it helps. Take care and regards.