Thank you for the follow up information - this is very helpful. Here is some basic background information:
1. Herpes virus (HSV) comes in two forms - HSV1 AND HSV2
2. HSV1 is typically associated with oral cold sores and HSV2 is associated with genital sores (they are basically the same thing in different locations
3. HSV1 can be associated with genital sores AND HSV2 can be associated with oral sores
4. When HSV1 is associated with genital sores, the recurrences can be extremely infrequent
5. There can be transmission of oral HSV1 to the genital area with oral sex
6. He can have viral shedding of the virus from the oral area even in the absence of a visible lesion
When I review the picture, my first impression is that this definitely looks like a resolving herpes outbreak (it is a shallow ulcer with a surrounding red base). I have seen many patients with herpes and this is exactly what it looks like but I have also been wrong in the past as well. But given what I have explained above, I do not want you to jump to any conclusion about your husband or infidelity until you have all of the facts. Here is where you go from here:
1. Await the results of the HSV titers - if they are positive for exposure to either HSV1 or HSV2 in the past, then the most likely explanation for the sores is herpes
2. Assuming a stable relationship, the most likely source of transmission is viral shedding from your partner from an oral lesion
3. The MOST effective way to determine if this is herpes is to directly culture the sore but this is more effective slightly earlier in the process than you have shown me in the pictures.
Let me know if this answers your questions.