Sudden swelling in neck

Sun afternoon i was bathing my Peke with Malesab shampoo and he started acting unusual then his neck started swelling.He was acting very off balance and his color was getting pale.I immediatley gave him a tsp of Benadryl ,he weighs 12.6lbs.I rushed  him to the E.R. trying to keep him alert.When we arrived the swelling had decreased maybe 20%.It looked as if a baseball was under his skin right below his ears.Also it looked like a Charlie horse half way around his head.The Dr on call wanted to send him on to U.T. in Knoxville for surgery right away.Sh also detected a grade 4 heart murmur.An hour later there was a shift change ,The next Dr said that since he was walking around and the swelling was subsiding that i could wait and see my regular vet the following day.His x-ray showed narrowing of the C2  C3 area.She heard a grade 2 1/2 to 3 murmur.I brought him home the following morning,He was still a little swollen,But acting normal.His regular Dr and another Dr in the clinic could not detect any murmur,So there was no need for any EKG or ultrasound.Also the swelling in his neck had almost completley subsided.There was no ruptured disc at all. My Question is,What could have caused all of this.Also how can there be a murmur detected and then it be gone.Can  extreme pain  be the cause of that?Any opinions would be nice?

[Kimberly Coyner, D.V.M., DACVD]

This is not a skin issue and I recommend that you re-post it in the Pet General Health Issues section. That said, acute swelling of the neck and pale gums could indicate a severe allergic reaction, and I do not recommend using Malaseb shampoo again just in case. A herniated disc does not cause external swelling that you can see or feel, it causes pain/stiffness in the neck or back and wobbliness or paralysis in severe cases.  The rapidly changing heart murmur may have been related to abrupt changes in blood pressure if it was an allergic reaction or shock, but there are alot of odd unrelated symptoms that you are describing, and I think an examination by the internal medicine specialists at UT is a good idea to get a different perspective.
Good luck,
Kimberly Coyner, DVM DACVD

[chasha33]

The E.R vet was the one who told me his disc was ruptured.My vet said that there was narrowing of the disc.Thankyou so much for your time...

[chasha33]

Thankyou so much for your opinion and you time.May God Bless You.