Why is my female dog's mammary gland suddenly swollen and not painful?

I can see that Ginger's mammary gland is rather swollen. It is a little difficult to tell from the photo, but there may be somewhat of a lump under the skin. While swollen mammary glands are definitely a sign of pregnancy, a false pregnancy, which results from a hormonal imbalance can cause this as well. I recommend having Ginger seen by a vet for an exam, particularly because certain cancers can appear this way. They can also determine if she is pregnant, or provide you with options on how to manage a false pregnancy at home. I hope all is well! Thank you for using Petco Pet Education Center, formerly Petcoach!

I am sorry to hear about Chocolat. There are numerous possible causes for this swelling. These could include a pseudopregnancy (where the body for some reason thinks it is pregnant and starts producing milk), mastitis (an infection of a mammary gland), mammary gland hyperplasia (a noncancerous swelling of the mammary tissue), tumors of the mammary gland (not common in dogs this young but not impossible), or a benign tumor such as a fatty tumor such as a lipoma that just happens to be over the area of the mammary chain. I would recommend an exam at your vet to help determine the cause and appropriate treatment. They may recommend an aspirate of the area with a needle to help identify what the cause of the swelling is and how best to treat it.

Unspayed dogs can be prone to mammary tumors, which causes swelling and pain. Fifty percent of these mammary tumors are malignant, so you will need to take Mocha into a vet first thing in the morning to have this examined and diagnosed. Once the cause is found, the vet can discuss treatment options with you. Best of luck.

In an older dog a swelling like this around the teat is most often a mammary lump. 50% are benign and 50% cancerous in dogs. They can be closely linked to hormones hence the fluctuation in size. Other causes would be mastitis or mammary development, but this photo does look like a lump. It can be tested by the vet to know what sort it is.

I have never seen a bug bite cause inflammation of a mammary gland. Swelling is usually from mastitis - some type of infection and/or inflammation got into the teat. Please take her the vet for an exam. The vet needs to see her in person.

This swelling is probably a hormonal response to being in heat. As long as she still has hormones in her system the swelling will remain. Since your vet did not feel like it was anything significant, it is probably fine. It will eventually go away on its own and if not it will certainly go away when you spay her. If you feel like the swelling is getting larger or starts to feel firm or painful than I would be concerned. Otherwise it is just a side effect of her being in heat.

Thank you for submitting your question regarding Bella. The pups may not be nursing that gland as often resulting in engorgement. I recommend encouraging the pups to use that gland. The other concern I have is that mastitis could be starting. Ideally she should see her veterinarian to ensure that this is not the case. I hope this information helps!