If a person wakes up and finds some wetness, one of three scenarios must apply:
He is certain that it is maniy, in which case he must do ghusl, whether he remembers having an erotic dream or not.
He is certain that it is not maniy, in which case he does not have to do ghusl, but he should wash whatever it got onto, because it comes under the same ruling as urine.
He does not know whether it is maniy or not. This is subject to further discussion:
(i) If he remembers having an erotic dream whilst he slept, he should regard it as maniy and do ghusl, because of the hadeeth of Umm Salamah (may Allaah be pleased with her) when she asked the Prophet (peace and blessings of Allaah be upon him) about a woman who sees in her dream what a man sees – does she have to do ghusl? He said: “Yes, if she sees water.” This indicates that it is obligatory to do ghusl for one who has an erotic dream and sees water (wetness).
(ii) If he did not see anything in his dream, if his sleep was preceded by thoughts of intercourse, he should regard it as madhiy. If his sleep was not preceded by such thoughts then there is a difference of scholarly opinion.
Some said that he should do ghusl so as to be on the safe side.
And some said that he does not have to do ghusl, which is the correct view, because the basic principle is that a person is as he originally was.
End quote from Fataawa al-Tahaarah by Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him), p. 221.
The fuqaha’ have stated that the smell of wet maniy is like the smell of dough or the pollen of date palms, and the smell of dry maniy is like the smell of egg whites. Mataalib Ooli al-Nuha (1/162).
It makes no difference whether that happens once or twice a week or more. Every time you experience a wet dream you must do ghusl. You should not get worried because this happens, because the reason for it may be that this is the nature of the body, or some kinds of food, and so on.
And Allaah knows best.