Are there any side effects of masturbation in men?

It's safe & healthy. Claims about it "lowering sperm count" reflect less resorption of fluid if you ejaculate often. Claims that it will make you insensitive to the humanity / feelings of others are based on ideology, not real life. Claims about acne and other physical woes are just untruths. If you're obsessed with erotica & missing out on other things you should be doing, a bit of medication / therapy will help.