Hi! I'm 31 year old guy and I have suffered ichthyosis vulgaris for all of my life. I don't want to raise any big expectations but I would like to share something I have done to make my skin better. There has been little improvement in my skin, but it's long way that I can believe it. It is also possible or even probable that improvements disappear.
One thing that has reduced most is flaking. My skin is still very dry and I'm at the moment waiting greases to absorb.
I use basic lotion but I have mixed there about 5-10% of sodium PCA. I also take above-mentioned stuff internally (couple of sips a day). Now I must say that I'm not aware of all medical influences what might result of using these products.I only like to share my experiments.

In addition I use lots of natural products. Espesially different kind of oils. Flax seed oil, fish oils, buckthorn oil and evening primrose oil. I also take glucosamine, bethaine, carnithine and diatomite product. I eat lots of fruits and berries. For example dark grapes, watermelon (white stuff includes lots of citrulline) and blueberries. Lately I' have start taken Aloe Vera juice.

Then there is something I try to avoid. These things like many that I have mentioned above are things that I have found right from here (ichthyosis forum). So I try to avoid caffeine, then there is nicothine, then alcohol. Lately I have started avoiding wheat, rye, barley and oat. Before I also drunk about 1 liter milk in a day. I don't do that anymore. (I think I also have lacthosis intolerance and avoidin milk makes me feel better).
It isn't clear what effects positively to my skin but one thing might be the better condition of intestines. On guess is those omega fats. Last but not least is internal and external use of agents that are lacking in ichthyosis vulgaris skin: Pyrrilidone carboxylic acid and, Citrullline.
Trans-urocanic acid is one component but i have no experiences about that.

Link about fliggrin metabolism

I don't take any responsibility of causes if someone likes to try my guidelines. I'm not a doctor. I just try to found something which makes this skin disease little less annoying. I also would like to hear if somebody has found something new information of this disease or has new even unorthodox way to treat it.

And never give up hope.