If your friend is serious, he has a problem: his biotin remark is nonsense.

Whether he has or will have a problem from eating too many eggs is another matter. If he eats two a day, he would have to have something seriously  wrong with him to come to any harm; If he were to eat two twelve times a day over a long series of days, he would be looking for trouble.

In themselves eggs are an excellent food, and we eat more of them than we realise, because we get them in more foods than many of us other than the likes of Nicholas suspect. However, there is no excellent food that cannot be overdone, even by a "typical, healthy person". 

How many are too many? An occasional binge is unlikely to hurt anyone with no special health problem. A daily dose of say, four to six eggs in a diet rich in roughage and fresh vegetable material, might be all right, but whether to would be a good idea, is another matter, either for your digestion, your circulation, or any sensitive person sharing your dwelling.

Did your friend mention "egg white disease" & vitamin H ?

I think it's mostly/completely bollocks ~ all those mail order & high street pill-pushers [chemist shops & health food shops]  rely on a fearful & gullible public

Michael

Well Michael, I agree about most of the bollocks, but it has been well known for a long time that raw egg white does contain avidin, a protein that  binds to biotin vigorously enough to cause a dangerous deficiency if you eat too much raw egg white for too long. I went on line for some details and found at least one zealot swearing by as many raw egg yolks daily as you could swallow, more or less, but consigning whites to biological warfare.

Now, I reckon that you can eat as much cooked egg as your body feels comfortable with, with very little risk, though I am not all that comfortable with so much cholesterol (I doubt it does much harm, but...)

My unfailing tune on the megaphone remains: eat it in comfortable quantities, tgether with comfortable quantities of other foods, taken together with exercise and good cheer.

And I don't care a fig (especially not a ripe, sweet, aromatic, tasty fig!) who disagrees.