Robert Downey Jr. thinks good hygiene is the key to a happy marriage.

The 'Judge' star has been married to film producer Susan Downey, who is due to give birth to their second child next month, for nine years and he thinks his wife appreciates his love of showering.

The 49-year-old star said: ''This is one of the keys to our relationship. I am so clean you could eat off of me. I think women appreciate that.''

But Susan, who has son Exton, two, with the actor and is expecting a baby girl, believes the secret to their successful relationship is knowing when to give each other time and space.

The 40-year-old beauty told PEOPLE.com: ''It's also about knowing when your partner needs a little 'me' time.

''That's key in any relationship. Whether you're working together all of the time or not, you always have to give each other space and kind of read it. ''

She added: ''He's a little bit of a slower start in the morning than I am. So I have to make sure that there's enough coffee in his system before I start throwing questions his way.''

Robert also admits he is mesmerised by Susan, 40, when she dances.

He said: ''She dances. So when she gets her dance time on the dance floor with the other girls ... It isn't Jazzercise, it's real dance! When Mommy is done dancing, the world is a better place.''