Answered by Shaykh Amjad Rasheed
After having performed a ghusl (purificatory bath), how do I differentiate between the exit of my husband’s sperm and the exit of my usual white discharge?
One may be able to distinguish between sperm and discharge by noticing the smell. If it has the smell of dough, then it is sperm, and if not then the default is that one does not have to rule about it after it exits from one again. This means that if the person has doubts about what it is, it is permissible for him to consider it sperm such that he must take a ghusl for it, or he may consider it something else, so that he must only perform wudu and wash the part of his body that was affected by it.
Amjad Rasheed
[Translated by Sr. Shazia Ahmad]