1. Selecting and blending alternatives

2. ……..Synergy This can exist on a number of levels:
Within the plant – e.g linalool and linalyl acetate – both sedative (Rhind 2012)
Within a blend of essential oils – Sesquiterpenes & esters – anti-inflammatory (Battaglia 2003)
Between essential oils and carriers (Rhind 2012)
– arnica oil and rosmarinus officinalis
Synergistic/antagonistic aspects of therapeutic relationship (Harris 2002, cited in Rhind 2012)
Aroma v physical benefit (Harris 2002, cited in Rhind 2012)

3. Other Blending Approaches
BOTANICAL
Plant families – often blend well
Plant part (Steiner; Mojay; Lavabre – in Rhind 2009)
Roots – nurturing, grounding, warming
Leaves & Stems – physical and emotional respiration
Woods – respiratory system, balance
Resins – balance, inner core, inner peace
Grasses – nurturing, emotional support
Flowers – sensual, creativity, reproduction
Fruit/seeds – energy, stimulating, new start

4. If it doesn’t work!!
If the essential oils you have selected don’t actually blend very well there are a number of rescue measures you can take before deciding to throw the mix away and start again!
Blend Equalisers. 
Smooth rough edges – e.g. citrus oils, resins, pine, melaleucas
Blend Modifiers.
Strong aromas, give “oomph” – personality - e.g cinnamon, peppermint, chamomiles in small quanities
Blend Enhancers.
Less powerful than modifiers – e.g.geranium, cedarwood, may chang

5. References
Battaglia, S (2003) The Complete Guide to Aromatherapy 2nd Edition. Brisbane The International Centre of Holistic Aromatherapy.
Rhind, J P (2012) Essential Oils. A Handbook for Aromatherapy Practice. London. Singing Dragon