What sort of collar does he wear?
if it's a CHOKE-Chain or PRONG, or anything which is in any way painful or aversive, it will make this worse.

an all-fabric sighthound style martingale, at least 3/4th inch & preferably 1.5-inches wide, would be good -
or an equally-wide leather collar of the same type.

alternatively, a FRONT-clipped H-harness will allow U to turn him away from his intense focus on another dog,
which helps enormously to limit his arousal by cutting-off the staring contest before it begins.

a habituated headcollar is another good choice, but it cannot simply be put on him & used;
it takes an average of 5 to 7-days, wearing a headcollar more-often & increasing duration, to accustom a dog
to the funny-feeling of a noseband; just as we must GET USED TO wearing glasses [sunglasses, reading, etc]
for the first week or 2.
additionally, the headcollar is deliberately PAIRED with happy things:
first with meals only 2x each day; then with walks AND meals, the leash on the other collar;
then with any other fun events AND walks AND meals... until the mere sight of the headcollar has the dog jump
to his feet & run over to shove his own nose into it.

the dog is actually TAUGHT from the beginning to slip their own nose into the noseband - for a treat, each time.
the very-first time he sees the headcollar, it can be on the floor & treats put inside the open straps...
the dog's own kibble can be used, or any TINY high-quality pea-sized goody: meat, cheese, veg, fruit.
every time it is held up, s/he TARGETs [touches] the headcollar & gets a treat... then it becomes,
stick Ur nose in the hole to get the treat. then HOLD the nose in the hole... then STAND while i fiddle
with the neck-strap, wearing the noseband for a few seconds... etc, etc, etc.

__________________
terry pride, APDT-Aus, apdt#1827, CVA, TDF
*wolves R wolves, dogs R dogs, + primates R us.*
tmp, sept-2007

Hiya, the following may help

Flying Dog Press - Suzanne Clothier - Handling On-lead Aggression

Headcollars, types, introducing one (or muzzle), and walking a dog on one here:



Black Dog Head Halter

Agility Warehouse | Dog Agility Equipment and Supplies | Black Dog Head Halter

The Canny Collar

The Canny Collar - The Best Collar to Stop Dogs Pulling on the Lead - Home


The Dogalter

http://www.kumfi.com/index.php?page=...hk=1&Itemid=26

The DogMatic

Dogmatic Headcollar

Gentle Controller

GenCon All-in-1

The Gentle Leader

The Gentle Leader at Canine Concepts

The Halti

http://www.companyofanimals.co.uk/halti.php

The K9 Bridle

K9Bridle - The Worlds First Dog Bridle, Head Harness, Head Collar

The Newtrix Easy Way

Angela Stockdale, Dog Aggression Specialist - About Angela: an aggressive dog is an unhappy dog



http://www.apbc.org.uk/system/files/...headcollar.pdf

http://www.deesdogs.com/documents/wa...headhalter.pdf


Dogs like this need either 1:1 help or a class that specialises in grumpy/growly dogs.

HTH

i introduce it with treats BESIDE the headcollar, on the floor; then treats for TOUCHING the headcollar,
as i hold it; then TARGET the noseband as i hold it, TARGET the opening as i hold it,
stick one's nose INTO the opening as i hold it open, Keep one's nose in the nose-band,
then keep one's nose in WHILE i slip the neck-band ends together, then while i HOLD the ends together,
& finally while i BUCKLE the ends for a few seconds.

Desensitization To The Gentle Leader Head Collar - YouTube

Muzzle Training - YouTube

Desensitizing Your Dog to a Muzzle - YouTube

Teaching A Dog To Wear A Muzzle (Muzzle Training) - YouTube


then the dog wears it:
- only while eating for 2 or 3 days
[fill the bowl, call the dog, ask for SIT, put it on, SET THE BOWL DOWN, when the dog finishes CALL THE DOG
for 'dessert', "sit" - remove the headcollar, PRAISE, reward, release].

- then wears it FOR HAPPY EVENTS plus meals,
for another 2 or 3 days: leashed walks, games, petting or grooming - anything the dog enjoys,
but the leash is on the OTHER collar / harness for control; the headcollar is only worn for habituation
& happy associations.

if the dog likes car-rides, that's fine - but SECURE the dangling clip for the leash, safely out of reach!
or the end will almost-surely be gnawed-off while the dog is not watched, in the back-seat, making the headcollar
useless, or into an expensive neck-collar. Oops.

- finally, one day the dog Alerts happily when s/he SEES the headcollar come out:
they approach, shove their head into the noseband impatiently, wag & wiggle, & are full of happy anticipation -
'Where are we going? What are we doing?' is the dog's obvious message.

FIT it properly:
with the Gentle Leader, fit is especially critical: the NECK strap must be high & snug.
it should be as close to the ears as possible, & NO FINGER should fit under it!
think of a watchband - that's the idea; it should not rotate, nor slide-down, but stay put.

that SNUG neck-strap allows the NOSEBAND to be adjusted as large as possible, SET so that the lower
edge of the noseband barely reaches the upper-edge of the leather of the dog's nose.
this precludes the dog thumbing it off: it won't give sufficient slack to go over the nose & off.

NOW - clip the leash on the noseband, & go for a short, happy, brisk 1st-walk -
5-minutes is plenty, & that may be too long; keep the dog moving, briskly!

The more opportunities the dog has to stop & fuss at the collar WITH THE WEIGHT of the leash on the noseband,
the more likely s/he is to be suddenly resistant or unhappy with the headcollar; DON't use the usual leash
if it has heavy hardware, or it's an extra-heavy leash; it's overkill & not needed, a light leash & small
but sturdy clip are all that are needed, with a headcollar.

a BULL SNAP, or any oversize hardware, or a double-thick nylon leash, or an extra W-i-d-e leash, etc,
only add needless weight & will make the dog uncomfortable, as that weight is transferred to their nose.

a 6-ft long standard nylon leash, one-half-inch wide, will easily handle dogs up to 80# on a headcollar.

i use veg-tanned 6-ft leather leashes, 3/4-inch wide, for dogs over 90#.
LIGHTER is better - so that the dog does not try to thumb-off the noseband, but happily moves along.

__________________
terry pride, APDT-Aus, apdt#1827, CVA, TDF
*wolves R wolves, dogs R dogs, + primates R us.*
tmp, sept-2007

totally agree with leashed for life- don't label him as aggressive. rarely are dogs aggressive, normally it's frustration, lack of good long exercise and mental stimulation. Keep the muzzle on for the time being but above all KEEP CALm. The worst thing you can do when you see another dog is to tense the lead, he will automatically assume there is danger or you are frightened so may try to protect you. Keep calm, breathe, and try to read the signs of his own tension- tail tensioning, ears pricked and body tense then correct this- distract him in some way. It's easier said than done, and this will take time to correct. I would also recommed training classes of some kind so he gets used to dogs more in a controlled setting where you can correct the unwanted behaviour and allow him to become a well socialised dog who is polite!!