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Plasters, gauze, fabric tape, bandages (in all honesty, if they had an injury bad enough to require a bandage I'd take them to A&E but sometimes a bandage can stop the tears from a grazed knee better than anything ) micropore tape, burn spray, Arnica, Savlon, the Germolene with a local anaesthetic in it (v. good for numbing the skin a bit when removing splinters), tweezers, that paint-on pretend skin stuff (don't use that on the kids though - it's stings), antibacterial spray, antihistamine, insect bite/sting pen...
germoline arnica cream - a godsend plasters - different sizes, some waterproof, some without the padding. Calpol for head bumps thermometer scissors paracetamol/ibruprofen - for us adults Cotton wool antibacterial handgel Savlon/dettol
Anything metal (tweezers, pins, thermometer, scissors) shouldn't be kept in a first aid box, it should be in a separate container, even just kept next to it is fine. Medications should also be kept separate. Roll plasters aren't sterile and water proof plasters aren't good for the wound.
Mepore and Melolin pads I don't think anyone said.
Can I suggest you have a look at websites like St John Supplies or SP Supplies and see what they put into their kits. They do kits for every size - handbag (used to be able to get bumbags, don't know if they still do them), glove box, family, sport, different office sizes, duty kits etc.
Actually, while I wouldn't get a kit from a shop, I would be happier about buying one from St John Supplies or SP Supplies because they're not so marked up.
I have 2 (kind of) home first aid kits. In them I have
In a sweet tin type tin (which is more my medicine box: Adult medicines inc: sudofed paracetamiol ibuprofen throat sweets beechams powders
Adult/child medicines anthisan verucca seal & heal blue inhaler & spacer (v rarely used) zovirax blisteeze
Child medicines calpol 6+ calpol melts nurofen for kids chesty cough medicine piriton (past expiry date about 3ml of tickly cough medicine (past use by date ) list of doage instructions
"First aid stuff" tweezers Dettol wound cleansing spray stuff underarm thermometervarious plasters (mostly odd shapes/too small/too big as the useful ones have been used) micropor tape nail file lighter (just so we know where it is for candles in power cut)
In my proper (shop assembled; 5yo; probably out of date first aid kit in a proper green box I have - according to contents list on back:
Pair of sharp scissors (well they look blunt actually - but never tried them Assorted plasters (all been used; now in my other tin Cleansing tissues
Traingular bandange 3 small wound dressings 1 medium wound dressing 1 large wound dressing Micropourous tape (which is about 0.5cm wide so useless really) 4 burn pads (2 sizes) 1 crepe bandage 2 pairs of vinyl gloves 6 safety pins (actually I think these have found their way into my sewing box) 1 burn aid dressing 1 leaflet 1 wall fixing kit
And I have just checked and that lot went out of date Feb 2006
Actually on a serious point; don' buy unnecessary creams and lotions and potions as you can see some of them go out of date before you use them