A complex bio-polymer originating only on Arrakis. Its several biological activities include interaction with various centers of the central nervous system (CNS), interaction with the immune system, and deposition within the sclera of the eyes. To date the biologically active portion of spice has not been isolated, although it is known that other portions of the molecule contain clycoprotein, a cupric heme and cinnamic acid.

The interaction with the CNS is primarily in the K”hliker-Kramptz center, which controls time- space awareness. In most humans this center is rudimentary, consisting of only a small number of cells (K-K cells) in the central cortex of the brain. Ingestion of the spice stimulates the growth of K-K cells so that the individual becomes more aware of his time-space environment. It is due to the action of the spice on the K-K cells that melange is addictive. If quantities in excess of 2 grams per 70 kilograms of body weight are ingested, addiction is encountered. Withdrawal of the spice from an addict results in insanity and eventual death due to the action of the breakdown products of K-K cells on other cells of the CNS.

The geriatric properties of melange are considerable. The addicts predicted lifespan is increased two to four times that of normal, depending upon the age at which the spice was first ingested as well as the dose. When the spice is digested, certain as yet unidentified breakdown products are absorbed into the bloodstream. These products interact with T-cells of the immune system, rendering the addict immune to most bacterial, fungal, parasitic and viral agents of disease. Ingestion of spice also imparts an immunity to many common poisons.

One of the most striking results of a diet high in melange is the "Eyes of Ibab," the characteristic "blue on blue" eye color: the whites and irises of he eyes turn a deep blue. Visual acuity is not reduced by the deposition of the blue pigment. In fact, in the white sun light of Arrakis, the pigment acts as a blue filter, increasing contrast and enhancing vision. A melange addict will receive the advantages Immunity to Disease, Longevity and Acute Vision (when on Arrakis or other planets close to bright A, F or G class stars), once addicted the user can never safely discontinue use of the drug. If forced to withdraw, treat as per the disadvantage Terminally Ill with the character's expected lifespan equal to his HT in weeks. Unless the addict can gain access to the drug, insanity -- which would take the form of some or many of the following mental disadvantages: Berserk, Delusions, Compulsive Behaviors, Mania, Manic-Depression, Paranoia, Phobias, Split-Personality -- begins to set in at HT/2 weeks. Access to the drug will reverse some of these effects if the user is not completely gone. A crucial use of melange is to aid the Guild Navigators with the intricacies of space travel. The effects of spice upon the K-K cells in the mutated and highly trained Guildsmen allows them to `see' into the future and guide their starships around disaster. Some Reverend Mothers are reported to have a similar foreknowledge in conjuction with spice usage, but such talents are very rare and require extensive training to use effectively.

Melange is very expensive, and highly addictive. However, because of the preponderance of spice on the planet Arrakis, addiction to melange will occur naturally within one or two years of living there. It can be postponed a year or two by including many off-world foods into the diet, but is inevitable.

An addict requires two grams of spice per day. On Arrakis, melange is common enough in nature to meet an addicts requirements through normal food and drink. Off-world, however, it can cost up to 620,000 solaris the decagram.