Long review: I paid and ordered and was impressed with that part - the order arrived as it was supposed to, within the time frame stated on their site. I bought through MelanotanZA.
The product claims to tan you over three weeks. The biggest problem was that one nasal spray DID NOT last the full three weeks. By the time the spray ran out, I wasn't much darker than my original tan. Yes, I did go a little darker, but really, not much at all. I would say one shade only. The tan was so slight that my husband could hardly tell.
The one side effect is a mild feeling of nausea - I felt that for sure. I also got the darkening of the moles and spots - they say that these darken first and the skin around them darkens later. Well, that never happened as I ran out of tan spray. Also, a few extra moles came out - which they say also will happen - and these should disappear when you stop using the spray.
Now you also get Melanotan as an injectable - you can buy the powder, you have to mix it with sterile water and get insulin needles and then inject...seems like a major schlep to me...but perhaps that way would have worked more effectively. I don't know. All I know is that, for me, the nasal spray was a bit of a waste of money. Far better to use a tan can, a sunless tan cream or just lie in the sun.
If you're wondering whether this is a safe thing to use....here is a link to a video explaining how it works. It's a natural peptide - it mimmicks the body's own tanning melanin. It seems safe enough...although I don't know what long-term use of such a peptide would do.