Can't Delete Cookie being accessed from subdomains

[mateobus]

Hello,

I would like to create a cookie upon login that can be read on two different subdomains. I have achieved this. The problem that I am having is that I am unable to delete the cookie upon logout, as it can still be read even after it is deleted. Here is the code:

At login the cookie is set from a.mydomain.com:
c#

HttpCookie cookie = new HttpCookie("my_cookie");
cookie.Value = "test";
cookie.Domain = ".mydomain.com";
Response.Cookies.Add(cookie);

Cookie reading on subdomain (y.x.mydomain.com) vbscript

myVal = Request.Cookies("my_cookie")

Happens back at a.mydomain.com
Logout:

Request.Cookies["my_cookie"].Domain = ".mydomain.com";
Request.Cookies["my_cookie"].Expires = DateTime.MinValue;

However when I go back to y.x.mydomain.com, the cookie value still show up as what it was initially set to.

Can anyone shed some light onto why I can't seem to be able to delete the cookie.