my spouse always feels that oral sex is not hygienic
Well this may be difficult to convince someone who has some psychological resistance to engaging in oral sex that it is okay.
If some of the resistance is due to hygeine worries then perhaps a bath or shower before sexual activities would diminish those concerns?
Another suggestion is to use what is called a "dental dam" for engaging in vaginal oral sex. You may read about dental dams here.
But some people are just not into this sort of sexual activity and it might be very hard to convince your spouse otherwise.
Thank you for your question.