Hello and thanks for the query.
Although diabetes is very common cause for fissuring of foreskin,there are may more reasons for the foreskin splitting like

Inflammation – sore and red foreskin. Common causes include forced retraction, irritants such as bubble baths or dirty nappies.

Infection – the most common include posthitis and balanitis. Posthitis is infection of the foreskin, usually caused by fungus thriving in the hot and moist conditions. Balanitis is infection of the foreskin and glans, and is usually caused by poor hygiene. Smegma encourages the growth of infection-causing germs.

Chronic infections – for some males, posthitis or balanitis tends to recur. A complication of chronic infections is scar tissue, which could stick the foreskin to the glans and make retraction impossible. 

Phimosis – the foreskin is abnormally tight, which prevents it from retracting. This can cause recurrent balanitis because good hygiene is difficult or impossible.  Phimosis is the most common reason for circumcision after infancy.

Although medical treatment is advised and it is successful in many cases,the best treatment for repeated splitting of foreskin is circumcision( surgical removal of foreskin ).
Consult your doctor for the examination and his opinion.
I hope to have answered your query however you may revert to me for any further query.
Best of luck.
Thanks

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